The final task prior to hemming the trousers is to attach the buttons. Begin by laying out the button placement. I transferred their position on the fly first, setting their distance from the fly seam equal to the distance of the buttonholes from the fly edge.

Next mark the position of the front suspender buttons on the waistband. I like to make the first one about 2 1/2″ from the side seam, and the second one another 2 1/2″ from the first. Both are placed about 1/2″ below the top of the waistband.

Finally, mark the back button position about 1″ from the end of the waistband and 1/2″ from the top edge.

Attaching the Buttons

To attach the buttons, begin by passing a knotted thread from the wrong side through all layers.

Pass the thread through opposite holes of the button.

Make two complete passes through the button, passing the needle and thread back to the underside, and keeping the stitches rather loose. After this second pass, you can adjust the final height of the button by holding the button at the desired height and gently drawing the threads to the correct height. The height should be just slightly thicker than the suspenders or the fabric that will be attached to it.

The two stitches give just enough tension that the button will not move out of position, yet at the same time not be difficult to move if you want to.

After four or so stitches, begin making stitches in the other direction, forming a cross. The number of stitches depends on the strength of your thread and the thickness of the fabric. I’ve gone as many as six stitches in each direction.

Be sure to regulate the height with each stitch – at this point it’s impossible to change the height so any individual loose or tight stitch will affect the other stitches.

Pass the thread back to the right side one last time, and wrap the thread around the previous stitches 6 – 8 times, depending on the height, and pull firmly, forming the shank. This provides a durable finish to the buttons, helping to prevent them from falling off.

Finally, pass the thread through the shank three times in alternating directions to secure it, and trim the excess thread.

A waistband was usually found in the back of trousers to help adjust the fit as well as take stress off of the top of the seat seam.

Begin by cutting out two each of fashion fabric, lining, and optionally, linen. The linen is a good way to reinforce the belt, but is completely optional, especially if you’re using heavier fabric.

Place the lining and wool pieces right sides together, and then place that assembly on top of the linen, if using it.

Stitch around the belt using a 1/4″ seam allowance, and leaving a gap in the stitching about 1 1/2″ to 2″ for turning right side out.

A smaller gap means less hand sewing later on, but also makes turning right side out a bit more difficult.

When you get to the corners at each end, instead of making a sharp 90 degree turn, make a stitch across the corner as shown, giving room for the fabric when you turn it.

Trim the corners down to about 1/8″ to help in the turning process.

Turn the belts right side out.

I used a dull pencil to help get the points turned crisply.

Press the belt carefully after turning.

Close up the belt with a small felling stitch.

Repeat for the other belt.

Next, choose one belt to hold the buckle, and fold it around the buckle, basting it by hand with a couple of stitches. Mine’s turned under about 3/4″. Sorry I somehow forgot to take photos here but I believe it’s all in the video.

Then, getting your presser foot as close as you can, sew along the edge of the buckle, then out and around forming somewhat of a box shape to keep everything nice and secure. It’s helpful to use a piping foot here on your sewing machine, but I simply allowed the regular foot to sit on top of the buckle and turning the machine by hand so as not to accidentally sew into the metal buckle.

Next, buckle the belt securely, which makes laying the belt out on the trousers a little easier.

Lay the buckle on the trousers, the buckle centered over the split point in the seat seam.

Measure the distance from the top of the belt to the waistband on each side to ensure they’re at the same height.

Baste across the belt from end to end, being sure it’s in the correct position after basting. It’s a good idea to double check your measurements, mine were off slightly so I ended up adjusting.

When you’re happy with the positioning, draw a vertical line across the buckle where you would like the top stitching to be.

Top stitch around the belt edge and across the belt at the mark through all layers of the seat.

Here’s my completed belt after top stitching.

It’s a good idea to reinforce various stress points with bar tacks, especially if you have not done so on machine. I’ll be adding a bar tack to each side of my watch pocket, the back of the trousers at the split in the seat seam, and the bottom of the fly. You could also add one at the top and bottom of each side seam pocket.

Begin by knotting the silk buttonhole twist and passing it through from the wrong side through all layers.

Make a stitch about 1/4″ in length across the seam or area you are reinforcing, catching as many layers as you can. You could make it a prick stitch, passing the needle all the way through, in order to get through all of the layers.

I usually make a total of four stitches in place, but you could do more depending upon the thickness of your thread.

Now pass the needle crosswise between the stitches you just formed, catching some of the fabric underneath as well.

The number of these small stitches depends upon the length of your bar tack but eight seemed to work best in my case.

Pass the needle and thread to the wrong side and finish with a few back stitches in place. Here’s the completed bar tack, continue tacking the rest of the desired areas.

The bottom of the fly is tacked to give more strength to this very stressed area.

Here’s the watch pocket after tacking. You could do the side seam and open-top pockets in the same manner.

And finally but most importantly, tack the top of the seat seam just where the split begins.

At last we can begin to sew the inseams and seat seam, turning our work into something that actually looks like a pair of trousers. To begin work on the inseam, lay one leg in front of you, folded right sides together.

Pin the inseam together at the fork. There is a bit of excess fabric built into the pattern that needs to be fulled in here when basting.

Aligning the trousers at the hem, begin basting the inseam from the bottom towards the fork. Baste evenly until you get a couple of inches above the knees, or roughly two-thirds of the way to the fork.

You’ll notice now there is some extra fullness in the seat of the trousers that needs to be fulled in to the inseam. Continue basting towards the fork, carefully distributing the fullness as you go.

Here’s my inseam after basting. You can see the fullness that has been worked in. For that last little fold on the right side, I’d say that was a little too much fullness and to go back and baste that area again.

Place the trousers on the ironing board, back side up, and gently full or shrink out the extra fullness that was basted in using a bit of steam as necessary. As your pressing the iron in small circular or back and forth motions, the fabric will gently shrink away. Try to keep the iron within an inch or so from the edge to avoid shrinking more of the trousers than we want.

Sew the inseam by machine or using a back stitch (or back and fore stitch), keeping a 1/4″ seam allowance.

Remove the basting stitches and press open the seam from both sides, using a pressing roll as necessary.

The Seat Seam

Moving on to the seat seam, this step can be a little confusing – I almost always get it mixed up. Turn the left side of the trousers, with the buttonholes, right side out. Turn the right side of the trousers inside out.

Then insert the left leg into the right leg, so that they’re right sides together. Roughly align the seat seam at the fork / side seam as best you can. This makes sewing the seat seam a little easier than if we had done things the opposite way.

Line up the side seams at the fork for each half as closely as possible.

Now baste the seat seam together from the side seam to the bottom of the fly, or just beyond it for more stability. Be sure that the cut you made during the fly construction lines up with the bottom of the button catch. Smaller basting stitches are best to keep things from moving around.

The completed basting here stabilizes the seat seam so we can move on to basting the rest of the seam now.

Aligning the backs of the waistband first, baste from just below the waistband to the fork at the side seams.

Make a mark on the inner side of the seat seam (I’m showing the mark on the outer side in the photo) about 2″ or 3″ below the waistband depending on your size and preferences, to denote the opening of the back.

This will indicate the upper end of the stitching.

Sew the seat seam starting at the bottom of the fly through to the mark you just made. Sewing the area near the fly can be tricky due to all of the layers. Try to carefully manipulate and fold the fly out of the way to get as close as you can with your stitching to the bottom of the fly.

Then repeat the process and sew a second line of stitching almost directly on top of the first line. This will greatly strengthen the seat seam and help keep the seam from splitting open.

You can see how close I got to the fly seam here, it’s maybe 3/16″ off. If you can get closer that’s great but not strictly necessary as the fly will be secured further in a bit.

Here’s the same area from the other side. I realized I caught part of the seam allowance in the seam, but chose to leave it, as it’ll be pressed over in that direction anyway.

Here’s a section of the seat seam towards the back, you can just make out the two rows of stitching.

Finally, press the seat seam open from the wrong side, followed by the right side as usual. It’s somewhat difficult to get to all of the angles, so I use a tailor’s ham placed inside the seam and manipulate the fabric as necessary.

Topstitching the Fly

One last bit to do that I consider as part of the seat seam is to secure and top stitch the fly to the button catch, further strengthening the area and preventing the fork from tearing open. Lay the trousers right sides up, the fly facing you.

It’s hard to photograph, but align the fly carefully along the bottom, and baste securely through all layers. In the photo, I’ve got my left hand grasping the fly from underneath the fabric.

The fly after basting the lower area.

Now draw a small line across the fly, at least 1″ below the lowest buttonhole, to indicate the stitch line. This should be perpendicular to the edge of the fly, not necessarily parallel to the floor.

Sew across the width of the fly through all layers, being careful to not catch any other parts of the trouser underneath, such as the back side or the pockets. That’s happened to me all too often and it’s a pain to undo!

As there are many layers in this area, be sure to use a sturdy enough needle, at least a size 100. Even with that you may break a needle here depending on the fabric you’re using. Luckily this was a fairly light weight fabric and I was able to sew without incident.

I usually make two or even three passes over the seam for extra strength. You could also back stitch or side stitch this area if you feel up to it.

And the completed fly after top stitching.

It’s time to complete the waistband with a polished-cotton lining. Begin by laying your trouser half and lining out, right sides down.

Lay the lining on the waistband, right sides together, aligning one end so that it overlaps the waistband facing by about an inch.

Holding the lining in rough position with one hand, flip the entire assembly over so that the lining is underneath. Begin basting at one end towards the other, keeping about 1 inch away from either waistband facing.

As you baste, allow the fabric to curve over your hand. This mimics the waistband curving over your waist, allowing the outside of the waistband to be slightly longer than the lining, helping to avoid any excess fabric in the lining.

Here’s the facing basted in place.

Flipping back over to the inside of the trousers, trim away the excess lining from the opposite end so that it extends about 1″ beyond the facing below.

Now begin folding under the lower edge of the lining so that it’s even with the waistband stitch line, or just slightly below it.

Baste this lower edge in place from end to end, keeping about 1″ from either end.

Repeat with the upper edge of the facing as well.

The results so far. Now to finish up the raw ends.

Fold under the raw ends, aligning them as you prefer in relation to the facing underneath.

Baste securely.

Here’s the lining after completing the basting process. Now you can work on the felling without worrying about things slipping out of place.

Fell along the entire lining using a small 1/8″ – 3/16″ stitch.

One thing to note that’s not pictured here (I think it’s in the video), is be sure to not sew closed your watch pocket while felling the lining. I like to keep a couple of fingers in the pocket as I work to ensure that this does not happen.

Continue around the ends.

And along the top edge as well.

This completes the lining and waistband installation.

Waistband Buttonhole

One last thing to do for the waistband is to add a buttonhole similar in size and position directly above the buttonholes on the fly. Be sure to work it from the outside of the trousers, so that the nice edge of the buttonhole is what is seen from the outside.