Will this fit on a tripod/lightstand/hot shoe?

Yes!

Why didn't you use XYZ tool to make this easier?

I wanted to prove this was entirely doable with basic hand tools.

What's wrong with plywood?

If you've never worked with actual wood timber, I can see how this wouldn't seem like a big deal. But plywood is not even in the same realm of existence as timber. If you can, use real wood. Even a 2x4" from a big box store will do it, if you've got the tools to massage it into the shape you want.

Did you glue down the PCBs?

Nope. The wires hold the PCBs in place fairly well, and in case there's a problem down the road from wear and tear, I don't want to peel off glue. But feel free to use something like hot glue, if you're having trouble getting them to stay flat.

Why are your PCBs not 100% straight? Some are slanted.

The rotation of the LED won't have any effect on the lighting, and I wanted this project to reflect the normal build method of someone using plywood and hand tools. Crooked they are, because crooked they have a tendency to be. Could I fix it? Yes. Will I fix it? Prrrrrrrrobably not. Well, maybe. No.