Just have a thought on this design.
Inspired by Martyn, this design is definitely requiring miterbox method. Like the ancient pyramids where the point and base rely on connecting points to points, there must be a reference corner that will act as a one. That means we have to connect all the 6 sides of the box in a point to point design. Take a look at the plan below:
The TOP LAYOUT…
THE PERSPECTIVE LOOKING AT THE TOP VIEW
THE PERSPECTIVE LOOKING AT THE BOTTOM VIEW. This has given me a lot of thought how to connect those points and close it for integration. Well the posibility of impossibility will always stand.
HOPE, I can do these in flesh… Maybe veeners..
Anyone is free to copy and if you want an sketchup.. send me a pm.