Pull the seam back on itself and iron it flat.
Fold the bottom hem of the skirt over, iron it, then topstitch it. Then stitch along the top to gather the waist.
Gather the waist. Try to get it as even as possible.
Attach it to the botton of the bodice.
Make the sash by folding a strip of fabric over twice. Make it 1/4 an inch tall, about 4 & 1/2 inches wide. Put a little iron-on hem tape under each fold.
Smoothly place it around the waist, and cut away any excess. Temporarily hand sew the zipper in place.
It shouldn't be tight enough to constrict the bodice, nor loose enough to leave a gap.
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