Place the warped record on a flat surface.
Stack a pile of books or other LPs on top of the warped record to flatten it. Distribute the weight evenly on the warped record.
Wait for record to straighten out. This could take a long time to work properly, even months.
Place the warped record between two glass plates. Use this technique only if the record is severely warped.
Set the glass plates in the sun, using the hot to mold the record back into shape.
Watch the record and remove it from the sun after a brief period of time to avoid further damage.