See it in action at https://youtu.be/hAGahVimK18
I've split the body, so it could be printed flat. You can either print BODY.STL, or print separately the floor, the long sides and the short sides.
Pay attention to the small 0.5x1x2 mm pins on the floor - they are made for easier assembly of the model.
As for the round holes on the floor and the ram - they are supposed to be 1.75 mm diameter - the same as the filament - cut 5 mm pieces of filament and use them as pins.