Fill the balloon with water . This image illustrates why you don't completely fill the balloon you should always leave some room in the neck of the balloon, then as the form dries the pressure has somewhere to go and your clay wont split.
Make with model magic clay, contour to wrist shape and poke holes, then weave the rest of the bracelet. Cool handmade pottery bracelet--could be made out of glass! Just make a barrete on the cuff bracelet mold. Could make more than just 1 at a time.