I had one that I got at a garage sale for a whole dollar that was warped...
tried the wet towel/hot iron - didn't work...
lady here suggested tossing it outside in the hot sun for a few hours and that did work..
I brought it in and put in on the table with heavy stuff on it until it cooled off...
keep in mind, I'm in Alabama - I don't know if the sun gets hot enough in Minnisota to work! :roll: :mrgreen: