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
Mat would not lie flat after removal from packaging. I placed it outside in direct sunlight for several hours to soften it enough to remove most of the warping. Even after several days useage it still does not lie completely flat.