Sort of self explanatory, has a hole on the back to attached to Lego size pegs.

Printed on Bambu X1C PETG, 0.08 layer height with a 0.4 nozzle.

PETG very tight fit with shrink you may wish to scale up to 100.5%

PLA will probably fit nicely at 100%

Added Smooth version for printing face down with Bambu AMS or whatever MMU you happen to have and included Fusion360 f3d file