A Short Tutorial with Photos
Cut 1 1/2″ Strips of preshrunk fabric. Cut the length 2-3 times longer than the width of your onesie. Ex. If the onesie is 8″ that would be from 16″-24″ strips. The longer the strips, the more fluffy the ruffle.
Serge the perimeter of each strip. Sew a gathering stitch down the center of each strip without sewing the ends. Pull the gathering stitch to the desired fluff of ruffle.