"I Dig 3D" 6 Piece Puzzle

This is an interesting puzzle. I deliberately did not take a picture of it solved. It is more difficult than it seems. There are hundreds of ways to put the pieces together, but it will be EXTREMELY obvious when you get it right. Do not look for anything subtle. Please do not post pictures of it solved, keep the challenge open for others.

I wrote the openscad file, but this is copied from a puzzle that I found in my drawer from years ago. There was no author mentioned on the original. If it h