Just an 80x80x8 block to help properly tension the release sheet for my Saturn 4 Ultra 16k. It may work in other applications. I have no idea if it does.

It does not need a brim if your print settings allow flat prints without warping. I put one on just because. I used PLA. You use whatever you choose. It is not a critical item. I used .2 layer height, 2 walls, and 15% infill at my high speed setting so it would get done. 

I hope this helps you.