For example, since I've never seen/used an epoxy that sticks to polyethylene and the like, what I do is wrap it in some cling wrap to stop it from dripping everywhere and put it on top of my laptop power supply. It's an older one so it's fairly big and gets fairly warm. The down side is that if you have a large area where the epoxy is exposed it'll take the shape of the cling wrap, including any folds/creases.
Or now that it's winter, a suitable heater may also suffice if you can find a good location.