I’ve made similar coasters a while ago, just with a stone tile as the base. Despite having to endure a cup of hot tea every day, it’s holding up very well so far and stays clean.
The PETG did minimally deform after months of using it, which is both good and bad. On one hand it’s now formed in a way that perfectly fits the specific cup I use, but that also means that it’s become a bad fit for every other cup or glass.
Your comment about using TPU has given me the idea however to make the tile reversible with the current PETG on one side and Flex material on the other.
Or the opposite: We only need one of those randomizers that shuffles the unlocks between multiple games. Just imagine one that incorporates Factorio, Satisfactory, shapez 2 and maybe Dyson Sphere Program. You’d be set for life.
The factory must grow (into other games).