When I first took the mat out of the box it was sort of folded over to fit the box. I tried putting it under a heavy carpet with weight for a few days with little success. I then put it out in the hot sun for a few hours and it flattened out.
[...] it doesn't want to unroll. We have to be careful - since it is clear it is almost invisible (which is a good thing) but we continually trip on it. I hope over time it will lie flat