I've seen sites that say to cut them with snips, and others with a hacksaw & mitre box. I've tried both ways, the snips leave the edges where i cut wavy and warped, and using a mitre box & hacksaw ...

In addition to a hacksaw, miter box, and rubber cement, here’s what you need for the frame: You will need the following lengths (all in 1 1/2 inch, schedule 40, type 1 PVC): ...