The trick to these dresses is sewing with elastic thread in the bobbin. You simply hand wind (without stretching) the elastic thread in your bobbin and sew. I discovered this terrific video by Heather Ross as shown on the Martha Stewart Show. You can view it by clicking here.
If you have questions and are a local customer, stop by Strawberry Patches and we'll show you some samples and get you started with the supplies you'll need.
Thanks for the great question!
Encourage one another,