Here's a little 3d puzzle I created. After studying some on-line photographs of similar puzzles I made the pieces, beveled them and then used Blender's 'shrink' tool to make each indidivual puzzle piece slightly smaller (so that they would fit after printing).
I added a 3d rendering for prettiness.
5.978 w x
5.978 d x
2.354 w x
2.354 d x