When I made my own the roll I bought was rolled but flattened out easy enough.
I believe the old glass in light trick may work with a VERY keen eye and multiple checks though.

Oh my goodness, sorry NextoPin, I obviously didn't see your post!!

Firstly about making - most would call me mad and I am.
I browsed the bay for a cheap polycarbonate at the right thickness. Was £30 rolled for enough for 3 playfields worth. Thats $50 I guess??
I chose to drill holes for all posts, thus ensuring a secure fit and hopefully reducing dust. After one slight scratch on my first go due to cheap drillbits. I got it to fit pretty nice.

I do need to take it off again to make some holes slightly larger as some areas can 'bulge' but in areas that don't affect gameplay.

As far as long term use - it's held up fine, cant see any scratches or clouding but tbh we don't play as much as some might.
The only thing I would say is that there can be a few airballs and fast behaviour.

For our needs (cheap, not minding diy, kinda wrecked playfield as is) it is pretty perfect. I also have a template if I need to make again for not much cost.

But as some may have said, dust can get to areas. I assume this is worse with the ones you buy with larger holes for rollovers etc.

If your machine is in pretty good nick I'd look into clearing, even with varathane? I guess it depends what you're looking for.

Fair enough. It'd definitely do just to get that going.

As for making it, just a drill with various size bits, hole saw bits and a torch