I created this box that only fits together one way.
I started off with a standard cube.
Shelled the inside
Using multiple small sketches, I push/pulled the sides of the cube to create a staggered edge.
I created another cube slightly larger than the cube on the bottom and used the combine tool to cut the staggered edges into the top so that top would slide into the bottom.
Using the push/pull tool, I created a hole in the top. Copy pasting the bottom half, I scaled it larger, flipping it upside down and joined it with the top creating the same staggered pattern on the outside of the box.
Using sketches, I push/pulled a pattern on top of the top half.