The pots are easily knocked over, and the lids don't reliably stay open on their own.
I whipped this up in Blender, based on a design that I saw on the internet somewhere. It addresses both of those issues.
The broad splayed base keeps the pot stable, and the upright tab keeps the lid open. It's designed to take the larger pot size as well as the little 18ml ones, though I've heard a rumour that now that Citadel have reformulated their wash recipes, they might be discontinuing the larger (better value) size. I hope not.
The stand could do with a bit of refinement though — the upright is about 10mm taller than it needs to be, so that's just wasted printing time and filament.