Glass can shatter when it experiences temperature shock. Be sure that your glass is room temperature or slightly warm before putting it in the oven, so that it doesn't go from very cold to warm too quickly.

Slide your record, sandwiched between the two panels of glass, into the oven.

Stay with your record and watch it. If you smell anything funny or hear any strange noises, remove your record from the oven.

Warm your record in the oven for 2 or 3 minutes.

Leaving your record in the oven for longer may melt your record.