Use a couple of pins to mark the row of shirring you want to sit at your waist. If I had left some more at the top I would have had a maxi skirt, but the first tier didn't sit at a very flattering place on my hips.
Cut just above the elastic. You want to do this after the elastic is in place as the elastic helps hold the shape.
Roll the raw edge down folding the elastic to the inside of the skirt, and sew down with a zigzag stitch.
This is the new waistband from the inside. The zigzag stitch allows the elastic to stretch without pulling out stitches.
Voila! A lovely lightweight knit skirt for just $2!