If I wasn’t reusing the pockets of this pair of trousers then I would make them up first. Since they’re already made for me on the bought garment, I’ll start with the zip.
Overlock the front crotch’s separately.
Sew and back stitch the front crotch seam from the bottom of the zip length to the seam end.
Sew in the zip and attach the plaquet. (I have a sheet of instructions for this technique).
Note. This is the tricky time consuming bit, but it’s easier to handle the sewing if you’re only working with the two front pieces. If you make up the entire trouser and then put in the zip then there’s the potential for the back pieces to get caught into the sewing, and it’s far easier to sew on the flat without the bulk of the rest of the garment getting in the way!
Join the back crotch seam and overlock these together (gives added strength to the seam for moving and sitting).
With the front and back complete, lay these right sides together.
Sew the side seams, matching notches if you marked them.
Press all seams.
Sew the inside leg seams. Start at hem on one leg, sew across the crotch seam and finish at the other leg hem.
Press the seams.
Attach the waistband. I remeasured the pattern to get the finished waistband length. I reused the waistband from the bought trousers. I matched the centre backs of the trouser to the centre back of the waistband and pinned forwards in each direction from this. Only then did I cut off the excess from the waistband. I sewed on the waistband copying the way it had been sewn onto the original trouser.
Overlock the hem edge making sure the side seams face towards the back.
Try on and check the trouser is the correct length.
Sew the hem. I usually start at the inside leg so that the back stitching is hidden. I used a single line of machine stitching to finish the hem.
Choose the button and make the butttonhole. (I pick the button, add 3mm onto its length and this makes the length of the buttonhole. Sew the buttonhole, cut the opening. Mark the position of the button, remember the button will sit at the end of the buttonhole closest to the end of the waistband. The button will not sit in the middle of the buttonhole.
Finished and ready to be worn.