I have one of those things. Works fine on an old coleman that uses white gas, but doesn't get up to temp on my propane
camp stove. Yes I ONLY use it outside. Most of the time it's all packed up and on a shelf in the garage. Just too much trouble to take along. I'm already taking a stove AND a tabletop BBQ. When I do get enough heat into it it works well. It gets so little use that it's probably one of next years garage sale items for the Emily gathering.
If you try yours make sure to have lots of space around the pan. This lets the heat surround it. Too big of a pan and you have cool spots.
There aren't a lot of directions that came with mine. Here's what it says---
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1 Center oven over the burner of your camp stove.Protect your stove and oven from wind as much as possible.
2 preheat oven slowly and allow enough time for the desired baking temperature to become stableized.
3 Place pans or other materials, such as potatoes, in the center position of the oven. Do not use pans larger than 8 inches square or 8 inches in diameter.
4 Varying wind conditions and outdoor temperatures may cause baking time to change from that in your recipies. Use normal kitchen testing methods to determine when food is done.
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That's it. Have fun and don't get wet.