I made this this afternoon for my granddaughter. It is a size 4T and I used a pattern, but I used a pillowcase instead of reg. fabric.
I've tried making the other pillowcase dresses that are gathered across the top and they didn't turn out as well.
So for this one I laid the pattern pieces on the pillowcase and cut down to the ruffle, but didn't cut the ruffle apart. So the front and back were attached at the ruffle. I used the serger to sew it together.
I used little white flower buttons at the top.
flower button
[ATTACH=CONFIG]77920[/ATTACH]