This technique assumes that you're not in a hurry to reuse this record. Simply place the warped record at the bottom of a heavy stack (usually records). After some time, the record(s) will begin to flatten. Be sure that the record(s) is on a flat surface. The amount of weight on the record, the length of time under the stack, and even the room temperature will determine when your record becomes playable. In extreme cases, it may take years for the record to straighten.