So off I went to the Internet. Hot water or put it in the oven! Ok hot water is never going to get hot enough to bend and even boiling water from the kettle is only going to heat the acrylic and not flatten it. The oven well that just plain scared me with visions of melting acrylic and suffocating from the fumes.
So I suddenly thought what can I do to heat the acrylic and slowly flatten it. Eureka moment an iron and ironing board. So I heated the iron to its highest temperature covered the acrylic plate with a tea towel and then slowly ironed the acrylic plate. Every couple of minutes I would turn the plate and with an oven glove on to stop burning myself press down firmly on the plate. It took about 15 minutes working each side and pressing down until the plate straightened. I then left it on the side to cool.
So now I have two straight acrylic plates.
So this is my tip of the day iron your acrylic plates to straighten them 💜