Flattening a warped LP

I tried two polished 12-inch marble tiles in the 200 degree oven and that worked great! Stick the sandwich in the oven, turn it off and come back when its cool. You're good to go.

I put the sandwich in cold, but left the heat on for 30-seconds or a minute or so, then turned it off. Those stones take a really long time to truly cool down. About three hours to room temp. Not hot, just warmer than ambient temp.

just be careful not to move the vinyl around between the stones, and start with something you can live without in case something bad happens.