Ok, I just had to weigh in. Yes, you can make your own sheet acrylic. No it’s not worth it. I tried it once. Turned out terrible and cost me maybe ten times as much to make my own as to buy the comproable 24 by 24 by quarter inch sheet. It wasn’t perfectly flat, it wasn’t perfectly clear, and it wasn’t just bubbles inside but also weird swirling, looking through it was like a see through fun house mirror. Oh, and did I mention the fumes created don’t just stink, they will KILL you! I wore my $250 chemical mask from work, and although I didn’t smell anything I had a massive headache for days. Also, i has the shop door open and the next day every fly in the shop was dead on the floor. This is ABSOLUTELY not worth trying. The risk and cost is far too high.
One more note. Three inch acrylic is typically multiple sheets laminated. Also, unless you own a zoo, find other ways to use your money.