This is a box (without a lid).
It is designed to slide together and not come apart. To print it, your printer will need to be pretty well tuned in as it is designed with tight tolerances. No support material is required, simply print the parts and slot it together.
You will need to print two "box side" files and one of each of the rest. No support material is required and I printed it at 0.19mm layer height in ABS on a Zortrax M200.
This design was born more from having a spare five minutes than need but it was nice to see it go together so easily and be almost impossible to take apart again!