HELP creating geometric shape for 3D printer

[curious aardvark]

The weird bit that makes it strange to look at is that the trinagles on the long sidees lean outwards, while the upside down ones on the corners lean inwards.
And your brain doesn't believe they can meet up :-)

Tricky bugger - but I'm stubborn :-)

I made a video - first time I've ever made screen capture video. Windows game bar makes it dead easy :-)
it's fun :-)
And there will be more !