Weight it down for a day.

Probably. The rubber base has memory from being rolled up, but gravity beats memory if you give it time. Lay the mousepad flat on a hard surface, put a heavy book or two on the curled edge, and leave it overnight. By morning it should be flat.

If it’s still curled after 24 hours, use a hair dryer on low heat — wave it over the curled edge for 20-30 seconds, then weigh it down again as it cools. Don’t hold the dryer too close, rubber softens fast and you don’t want warping.

You might have to do this a couple times if the pad was rolled tight for months. But give it time.