Did you know that Lasse Holmes' Sidewinder (a type of batch box) can also be used as an oven?
Not the "warming oven" over the firebox, though that does work as described. (To re-heat, pre-heat, or raise dough, depending where you are in the baking/cooking/cooling cycle).
The firebox itself turns out to be a great place to bake a loaf of bread, or throw in some potatoes or yams for a future meal.
The only catch is, you have to wait for the fire to go down to coals, which usually takes over an hour from when you light it. (More, if you have 3 shifts of class participants and staff rotating through to make their coffee and pancakes, who keep feeding the fire...)
It takes some focus - and some luck - to coordinate timing so that, while cooking one meal on the range top, you have another bonus item ready to bake at the moment the fire dies down. We did not always get the timing right - fortunately, half-baked yams are pretty easy to finish up on the stovetop for a quick breakfast the next morning, and the only real "losses" were some garlic and turnips that got left in for many hours longer than they should have... really, it was probably for the best; who ever missed a baked turnip?
For a fast warm-up, and sheer dedicated frugality on tiny amounts of wood, you can't beat the outdoor rocket oven. We baked at least three times a week on it throughout the month-long peasant PDC, everything from pot roasts to sandwich bread to cakes and cookies to pizza parties... sometimes two pizza parties the same week.