Taking the challenge too literally!?!?
Has to fit in a 50mm cube the man says :think: Hard to get that part out of my head and ended up with the following box - eventually :o:C
Pic 1. At left - A mock-up to see how it might look and work out how I would hold it. Centre - Miscalculated the wall thickness and tried to go to far into the corner with a spindle-gouge - At least one part clipped my nose and I was so sure the jolt had snapped my gouge I wasn't game to open my eyes - but it survived :U At right - the template I used for the hollowing.
Pic 2. The adaptors I made to slip over the jaws - did the trick :2tsup:
Pic 3. The finished box - Scrub Stringybark (rhodamnia rubescens) with 2 coats of DO. (accidentally :B Note to self - do NOT use oil on shapes that CANNOT be buffed)
Pic 4&5 The inside :shrug: