I laid the onesie unsnapped and measured the leg hole opening, then doubled that length. I cut two pieces of the doubled measurement long by four inches wide.
Folded it in half, (hot dog style) and sewed it.
Turn and press.
Then I simply began to create an accordion style pleat around the leg hole.
Pin and stitch it in place.
Quick and simple!
I liked the look of the accordion pleat, more uninformed and orderly in my opinion,
but you could certain try it with ruffles or anything really!