My wife loves the classic line drawings found in old coloring books. As a child, she always drew pictures with objects outlined in black. I thought I'd try to replicate that style - but using some of the same imagery (e.g., holes, doors, sun, and clouds) found in my more projective work.
The boxes measure approximately 6.25 x 4.5 x 2.5. Because I was running out of desk space in my office, I also made wall-hanging versions.