1. Prepare the fly front:
- Interface both sides of the fly with weft interfacing in the non-stretch direction.
- On the WS, mark where the zipper stop will go.
- Baste the CF seam down to the zipper stop mark, backstitch then sew the rest of the seam with a regular stitch length, stopping about 1" before the cut edge.
- On one side of the fly, clip to the stitching line at the bottom of the curve so the fly's can lie flat.
- Zig zag the short curved crotch seam using a tiny stitch eg. 2.8 x 1.5, to the bottom of the extension.
2. Insert the zipper:
- Flip the garment and one fly to the R, leaving the other fly extended.
- Place the zipper face down next to the CF seam line, lining up the zipper tape with the CF seam and checking that the zipper stopper is on the mark or slightly (½") above.
- Stitch along zipper tape near CF seam, from the bottom up.
- Turn the zipper under so that the seam just sewn is exposed and stitch from the bottom up at ⅛" from CF (same side of the zipper is being sewn).
- Flip the garment to the other side so that the other fly is extended. Let the zip flop over onto it and pin in place. Stitch.
- On RS, place a pin at the zipper stop.
- Mark 1 ¼" from CF basting line down to the zipper stop then round the curve down to where the seam starts.
- Stitch from the bottom up, missing the zipper stop. Note that it doesn't matter if the zipper isn't caught in the top stitching as it is securely fastened to the fly fronts.
- Remove the basting and press towards the fold.