A simple, but useful and adaptable fire marker that can be contorted into templates for many of the most common fire spells and ranges:
A 60 ft wall of fire, a 20 ft circle for fireballs, a 15 or 30 ft cone for burning hands etc. Guaranteed to set your players alight.
I was looking for a long time for a simple flame marker to use in an upcoming battle but all models I could find were too complex or specific, so I thought I'd try my hand at making something, based on the flame design from Amish_Rabbi - and while I was at it I made it extendable and flexible, more as a challenge than anything. Print as many or as few pieces as you need, I find that leaving some gaps empty looks better but you do you.
I have not ever run into any issues with the prints but I do recommend you print the first layer slow, ~30mms