Thanks Marty. The pieces (3 of the 4) I had the most cupping on were thin pieces (approximately 5/16″). One of these was a piece that was highly carved (your “3 Corner Chip Trivet”). It cupped way more than the other ones. Probably the amount of carving on that piece was a factor also. I’ll try your suggested method to flatten the trivet. The 4th piece, which cupped only slightly, was a 3/8″ piece of aspen. Do you consider 3/8″ thin?