Before proceeding with the make up of the trousers, all "trimmings'" and "fit up" should be prepared.
The fly facings should be cut from excess cloth from the topside crutch area, to ensure harmony with the fly curve. The waist band is taken from either the folded or selvage edge, a length of, half the waist plus 7" for inlays, extension and ease. Side pocket facing can be located at the underside seat, and hip pocket jettings are cut from below the fork. All pieces are cut and the double apart from the french bearer which is cut to match the grain of the cloth.
The items for the "fit up" are as follows, two pieces of linen 5" square for crutch stays, four strips of linen 9" long and 1" wide for pocket stays and two pieces shaped for the fly facing and stiffener. One bearer button, preferable pearl, and six brace if required. Two hook and bar will be needed for the fastening, stainless steel is best. Side pockets are made from silesia 14" x 12" and hip pockets take about 1/4 yard, and a fob pocketing is 10" x 5". Canvas is used in the waistband to add support, the hook and bars are sewn through it. A steel zip is preferable, nylon is considered "cheap trade". Silesia or lining is traditional used in the finished waistband and curtain, although I do prefer silk plain or pattern matched to an italian cotton in the pocketing. This I feel adds to the luxury of the finished garment.
When the crutch stays have been basted in position the topsides and undersides should be overlocked. The darts are sewn out, and the fly pieces are assembled. It is preferable to make ready all pieces of " fit up" before assembling the trousers, the pocket facings can sewn to their bags and the fly pieces sewn to the linen.
The left fly piece I seam a long the outer curve to a linen companion, it is turned out and seam to the topside, making the fly facing, as shown in the above images.
On the right, the zip is sewn on first followed by the facing and bearer, the linen can be basted or held during sewing. The seams used for the fly are 1/4" inches as well as a 1/4" overlap for finish. Both seams should be pressed open with a hot iron.
For the first fitting I never include pockets, if I decide to raise or lower the waistband the pocket position would alter. The topsides are now laid on the underside and seamed together. Notice must be taken to ensure all balance and notches correspond, if they do not the legs will be twisted and an accurate fitting cannot be achieved. I tend to ease on my waistbands, especially over the hip, adding 3/4" total on both sides. I make my run hollow at the center front and sweeping up to the center back. This method of hollow and ease helps prevent the band rolling on corpulent figures. The bands should be stretch, shrunk and shaped before sewing, a hot iron drawn over the band in the direction of shaping a curve.
Now we are ready to to join the inside leg seam, the left leg is sewn first, match the knee and hem notches and seam off 3/8" to the fork. Remember if the figure have bow legs or large calf there maybe ease allowed between the hem and knee, pin in position and "full in" when sewing. Open both seams on the sleeve board.
Turn out both legs. It's now ready for shaping. I usually start with the right leg, folding the center crease line and pressing firm with the iron. Place a weight at the top and press down the leg. Shrink between the seat the knee, stretch over the calf and shrink the shin. The legs should resemble an 'S' shape.
When the legs are shrunk and pressed they are ready to be joined. fold the left leg inside the right and pin the forks together seam on seam. Starting at the base of the zip lap the left side 1/4 over the zip and sew back through the fork to waistband. I tend to sew this seam with a long stich for the fitting as it will be removed once the fitting is complete, it is hand sewn on the finished garment. Baste the fly closed and reach inside and baste the zip to the facing. Now baste the facing to the trouser front.
Simple add the hook and bars and baste up the hems. A final press of the trousers should be carried out in order to present a clean and accurate fitting.