Before we begin, I have to mention, this idea is totally stolen from someone else, but I can't remember who to give proper credit!
First, I gathered my materials:
20 & 25 mm gw bases, and some beads. Not pictured: cotton wool, glue, and a hot glue gun.
I glued two bases together to create a plinth, using a hot glue gun (which really did not want to stick, so it took several goes in some cases, where I'd not waited for it to hear up enough, or not used enough glue):
And then glued a bead to the top for the actual fire pot:
No, that's not an olive in the background, I wasn't sure until the last minute whether to use the smaller bead, or to use the larger bead cut in half. I went with the smaller one in the end, as it looked like it'd be the right size for an adventurer to kick off of the plinth at an enemy...
Lastly, I took some cotton wool, and dunked it in diluted pva, and then using a cocktail stick tried to mash it into the top of the bead and sculpt it into a vaguely fiery shape. That didn't work though, as the cotton wool was far too wet, so I instead applied it dry, and gradually added the pva with a knackered old brush, until I had this:
Once the pva has dried, I'll give the tops of the plinths a once over with some basing paint to give them some texture, then a quick lick of paint and we're away!