I really like the Bahtinov Mask Generator by Brent Burton but my Flash Forge CP has a small print area so I designed one with a hinge. I figured it will store better in my box too.
Um, it can double as a napkin holder too.
I made it from scratch as I need the practice and I've included the STEP files so if anyone wants to improve on it or simply change the hinge (it's a 1.5mm hole now, so might need to change), feel free. If I got it correct, it should fit my Celestron Nexstar Evolution 8.
Update: It really works well.
Read about Bahtinov_mask at the wiki page.