This was mostly an experiment to see if I could design something like this in FreeCAD. Unfortuantely, I totally failed to take any photos of the finished product, OR the broken one!

I did get a report from my neighbour that it worked perfectly, but he was a bit wary of cutting the plastic directly with the mitre saw, so he cut it with a Dremel type tool. Which defeated the object a bit, to me :)

Yes, I am aware that you could probably make this out of wood, and honestly, I'm thinking that might be better in the future, but, it's done now, and it works. And the design just might help someone else. Although, it's not great.

I used the ironing feature for the top surface, which left it really quite smooth.

I didn't bevel any edges, but my edges didn't turn out very sharp - I had issues with the filament on the print - not enough for a failure, but it definitely wasn't extruding well.