Stack them, right side up, and cut in a random way with gentle curves into two or three pieces.
Then clip the in-curved piece about every one half inch, not going in quite a quarter of an inch.
Then you shuffle: I take the top left hand piece and put it on the bottom, and then take the bottom right hand piece and put it on the top. They're partially shuffled here.
Then line the pieces up, flip the in-curved piece over, and put a pin in the center.
Then gently pull the top piece so that the edges line up. The corners will not match; the top one will over lap about a quarter of an inch.
Sew as usual, pushing the fullness out of the way. On a gentle curve there isn't much.
When you get to the center remove the pin and rearrange the pieces so that edges on the rest of the seam are lined up. If a pucker seems to be forming, stop, lift the presser foot, and rearrange the fullness. On a sharper curve, you may have to do this a couple of times.
Do the other seam the same way, always putting the in-curving piece on top. You end up with three blocks, each one different. There was very little distortion on these blocks, but sometimes depending on the type of curve, there may be more. Trim them, and play with them.