first I closed the front crotch seam
then I folded it like it should in the end
the right centre front is the lower part
I folded it about 3mm parallel to the line and then placed the zipper
and pinned the zipper in place, just through one layer of fabric
sewed and folded it back over
pinned the slit shut and closed the zipper then pinned the other side of the zipper to the left front, also just one layer, sewed
and then sewed the decorative stitching on the right front
starts looking like the end result
now I needed one piece to lay under the zipper, and serged around the open edges
then pinned it to the lower end
then I sewed it close to the zipper
the finished fly.
I hope this was helpful for you. Let me know if you have any questions!
keep sewing and smiling