Stitch the seam below the zipper opening, backstitch. Press the seam allowances open. (Do not baste the zipper opening closed.)
Place the garment wrong side up on the ironing board. Preass seam allowances to the wrong side of the zipper area: ½" (1.3 cm) on the left or underlap side and 5/8" (1.5 cm) on the right or overlap side.
Place the zipper foot on the sewing machine.
Turn the garment right side up. Slip the closed zipper facing up under the zipper opening. Place the fold n the uderlap side next to, but not touching, the coil or teeth, with the bottom stop at the bottom of the opening. Starting at the bottom, stitch along the fold; backstitch.
Lay the overlap side of the opening on the zipper with the fold just covering the stitching. Center ¾" (2 cm) wide Scotch® Magic Tape over the fold to hold the opening closed and to provide a topstitching guideline. To topstitch the zipper, stitch across the bottom of the zipper, pivot, and continue along the guideline.
At the top of the zipper, backstitch.
Remove the tape. Pull the thread ends to the wrong side and tie in a knot; press.