How to flatten Vinyl Albums

I found the following suggestion on the web and wondered if anyone had tried it?

It suggests: cleaning the record;
placing it between two sheets of clean and perfectly
flat plate glass; heating to about 135 degs. F;
leave at this heat for 10 minutes;
remove heat and place some heavy books on top of the
glass for 24 hours.
If the warp is not removed then not enough heat
has been applied. Heat should not exceed 150 degs. F as damage may
occur.

I also heard this from a record dealer, but I have always tried to keep all albums away from heat