warped cutting mat

I have to confess I wrapped mine in a very damp tea towel and put it in a low oven for 15 minutes. Then I unwrapped it and put it under a pile of books. Two days later was flat.

I have a mat that warped, I put it under my matress for several months and that flattened it back out. I use it for cutting on, but not measuring. When I was looking online, people were saying that with the warping of the mat might mess up the measuring. Haven't been brave enough to measure and possibly mess up my cutting.

Everything I came across said not to use heat, but mine is fiskars.

I put a cookie sheet in the freezer for a day, took it out and put it on my cutting mat and weighed it down with books.