My cutting mat is 30” x 60”- always comes rolled. Luckily I only need to replace it about once every 10 years. When I get it home, if it’s nice out I lay it out on my sewing room floor - with a sheet under it, and a sheet over it. I place heavy books on the corners, sometimes sides too and usually one or two in the center. When it’s flat I put it on the cutting table which it fits perfectly. If the edges are still wanting to curl a little I put the books back on over night. I wouldn’t put it out in the sun- it might warp and never flatten.