I had one get warped in a move now I'm super picky and make them put it in a picture box and stuff around it. I tried keeping it between my mattresses for 6 months still couldn't get it to fix. Try and salvage any that does lay flat and have a small board and go get a Joann coupon and get a new one! Didn't know they were made of cotton cause their price sure when up to...Hahaha