Cut 3 - 2" x 44" Strips of fabric
Cut 2- 2" x 22" Strips of fabric
Take one of the long strips and sew the short ends with right sides together to create a loop. Press, and repeat with the other two long strips.
Leave the short strips as they are.
To create a ruffle: use a basting stitich (the longest stitch your machine allows) to stitch down the middle of each loop and both short strips. Leave the threads long on both ends.
Hold the fabric in one hand and the thread at the beginning of your basting stitch in the other (the top thread only). Pull the thread while moving the gathering to create an even ruffle around the entire loop. eyeball the finished size your ruffled loop will need to be to lay flat around the onesie.
Pin your ruffle around your onesie about 3 or 4 inches up, then adjust the gathering to fit nicely and pull to add or remove some gathering, if needed.
Stitch down the center of the ruffle all the way around, back stitching at the beginning and end. (don't forget to change your stitch length back to the standard size)
Sew the other two ruffled loops to the onesie with the seams only about 1/2 inch apart, to achieve a dimensional ruffled "skirt".
Now, turn the onesie over and attached the 2 short ruffle strips below the three you've already sewn. You can pull out the basting stitch if you so desire or leave it if you don't. Just trim up any extra long threads (like the one that's been driving me crazy in this picture) and you're finished.
P.S. You can serge the edges of the ruffles before you attach them if you aren't into the messy look like me :)