Poundland sell a three-legged canvas stool. It takes my weight and beats sitting on the ground when cooking.
We had a couple of those. The big one was stupidly heavy (at least a kilo), ever so slightly too long to fit in a pannier, and catastrophically failed to take my weight. My four-legged Coleman stool is superior in all respects, other than price.
The tiny one was better, in an uncomfortable sort of way, except I cut one of the legs off it to molish a cadence sensor bracket for barakta's trike. Which, as I've already pointed out, is the ultimate solution for comfortable seating while camping.