Update 2021-08-03 at bottom of post
Last week's game on the patio saw a few errant dice rolls, where, despite careful rolling into a handy tray, a few dice bounced off the table and nearly disappeared under the fence.
Since I had some sheets of foamboard lying around (thanks, Doug!) I did a quick search online for a dice tower pattern and found this one. https://www.instructables.com/Making-a-Formboard-Dice-Tower/
After a small amount of cutting and gluing (and a careless bit of finger slicing), I ended up with this.
It's not pretty, but hopefully will help to keep dice from scattering all over the place. I'll trial it next time I play, and if it performs well, I'll see if I can pretty it up a bit. The coloured balls are the heads of the drawing pins I used to hold the bits together as the glue sets. I'll see if the tower holds together after I remove the pins.