An old puzzle where you need to move the big block from the top of the puzzle to the exit at the bottom. The "exit" is marked by an indentation on the edge so you can distinguish between top and bottom.
This prints fully assembled, no assembly required. I printed at 0.35mm layer, but I expect any resolution to work.
How your printer is calibrated and the current thickness of your filament will affect the thickness of your print. So I've included 5 different STL's with an increasing gap size. Each STL has a number in it, this is the gap between the pieces in tenths of a mm. So start with 4 and increase or decrease that number if the print is too tight or loose.
4&5 work for my printer so I expect the range provided should cover most. Let me know if you need more.