My father-in-law asked me to design a few simple storage boxes for some of his ceramics tools, to replace some old boxes he had that were falling apart. So this is what I came up with. 

The internal dimensions are roughly:

• 183mm (~7.25 inches) long
• 58mm (~2.25 inches) wide
• 44mm (~1.75 inches) tall

I printed these in PETG, with 0.2mm layer height, and they turned out great—with the perfect amount of friction between the lid and the box. Just enough for the lid to be easy to pull off, while not slipping off on its own.

I recommend printing these with a brim, so that the corners don't curl and peel off the print bed.  No supports needed—just print with the flat sides down.