Hiya
Tried this having left Brian Auger - Black Cat on the turntable in direct sunlight. I preheated the oven to the required temperature & inserted the disk between 2 plates of glass - absolute disaster. Yes, the record flattened but was still unplayable not least because the grooves on the 'peaks' were flattened, but also because the record did not return to a completely flat state, more rippled.
It's now a clock in my kitchen, lol
Adrian