@dave some recs so far, use parchment paper around the baguette so it doesnt risk sticking to the inside of the tube. I made a full recipe(3 cups of flour) but split it in two separate baguettes(maybe less for your solar cooker). Its better to add less since the bread expands and could get stuck in the stove.
Also this is a no-knead overnight bread recipe.
There are more practiced solar stove bread makers out there, there's a few YouTube videos about it (and blog posts too).
@neauoire