Paper Princess and Quiltmouse have the right ideas. When I use the birthing method I always let the top go just a smidge over, we're talking tiny amount and it works perfectly. Another tricky time is when you are doing circles using the birthing method, such as coasters. I used to screw these up regularly until I found that if I cut them out on the bias there was just enough give to allow me to make a nice smooth closure without puckers.