1. I always starch my waistband pieces before I start. Use canned spray starch or home made. Fuse the interfacing to wrong side of the waistband pieces. If using very lightweight fabric fuse to both inside and outside waistband (so cut extra interfacing pieces). Use dry hot iron no steam for fusing. Join centre back waistband pieces together right sides together then join left and right sides to side seam of centre back waistband. Repeat for inside waistband, press seams open and they should be a mirror image of each other so when laid right sides together the match perfectly. Finish the lower edge of inside waistband by binding or overlocking (serging) now.
2. Showing both inside and outside waistband pieces joined. They are mirror image of each other.
3. For button fly facing fuse interfacing to wrong side of one half of facing. Press along fold line wrong sides together. One side of facing (here mine will be trimmed off left side) is wider so now press the wider part back over and sew down to conceal the raw edge when it’s sewn into the fly.
4. Showing the facing pressed and right side sewn down to conceal raw edge.
5. Mark for button holes and sew in using button attachment on sewing machine or by hand. Apply fray check to buttonhole centres, leave to dry then cut open.
6. Assuming these are for men the fly will finish left side on top of right side. Mark left trouser front with tailors chalk or pins the two fold lines of left fly and press to make a double fold. Pin and then topstitch down edge to small dot. (picture showing right side of left trouser front piece after topstitching)
7. Picture showing wrong side of left part trouser front). Open facing out and lay buttonhole fly piece onto inside of left fly so it’s just inside the edge of topstitching. Sew down edge (facing only not through main trouser fabric). Turn facing back under and pin into place.
8. On trouser right front fuse interfacing to wrong side of fly facing, mark the fold line of fly facing, either overlock or bind raw edge of facing to neaten. Fold on marked line and press to wrong side. Topstitch edge all the way then mark 40mm from edge and topstitch again
9. showing both front pieces ready to join together.
10. Lay front trouser pieces right side together and pin along the curved centre front seam to large dot. Sew reinforcing at the large dot.
11. On the table lay the trouser fronts right side upwards. The left side will have the fly facing pinned. Feel for the lower edge of fly facing and mark this with a pin. Starting from waist edge on right side sew down trough all thickness’s of fabric to fix the fly facing into place. Stop 25mm (1”) from pin marking bottom of fly facing. Keeping machine needle into the fabric until last moment to prevent movement raise machine foot and now slide the trouser right fly facing under the left piece so the bottom edges align. Once aligned raise needle and set down again and continue sewing to 10mmm (3/8”) from bottom of the fly facing edge you have marked with a pin. Turn to follow the angle of facing and sew through all layers to secure.
12. I sometimes sew a second line horizontally too for extra reinforcement. The fly front should be perfectly overlapping and meeting the join seam. Snip almost to large dot on inside curved seam.
13. Showing fly complete and fronts joined. Wipe any chalk marks off with damp cloth.
14. Lay front trouser piece onto back trouser pieces right sides together and pin outside seams. If adding any piping or decoration to outside seams do at this stage. Sew from waist to hem on both outside seams. Press seams open. Align and pin inside seams starting at crotch
and sew front trouser to back trouser pieces. Press seams open.
15. Neaten raw edge of inside waistband along lower egde either with binding or overlocking (serging).
16. Pin outside waistband to inside waistband along
top edge and join. Clip curves and any bulky seams. Leave ends open for now.
17. Showing clipped curves on waistband before joining to trouser.
18. Align outside waistband to trousers right sides together ensuring all seams match. Sew waistband to trouser keeping inside waistband out of the way. Clip seam carefully. Sew the ends of waistband as in picture so its perfect fit to the trouser at the ends. Clip corners and turn waistband through. Press.
19. I prefer to topstitch top edge of waistband before sewing though all thickness’s to conceal the join seam. You can do either way I just prefer this way. Topstitch around waistband top edge. Then pin and making sure the join seam is turned upwards into waistband sew from right side through all thickness’s to complete the trouser.
20. Mark for top button hole and sew it. Mark for all fly buttons and braces / suspender buttons on waistband and sew into place.
Try on and adjust leg length then neaten lower raw edges and hem up. Finished.