In a large bowl, combine the flours and salt.
In a large measuring cup, combine the warm water and sourdough starter or yeast. Stir until dissolved.
Combine the wet with the dry and mix until you cannot see anymore dry flour (a shaggy dough). Cover the bowl with plastic or beeswrap and leave it on the counter for 8-12 hours. Head off to work, go climbing, transplant some trees, whatever.
When you get home, turn out the dough onto a lightly floured surface, fold the dough onto itself from all four sides (pull the dough out, making "ears", then fold it in). Flip your bowl over and cover the dough. Let it rise for 1-two hours more.
At this point, the dough should have risen to about double the size. It is ready to bake. If not, give it another series of folds and wait another hour.
About 20 minutes before you are ready to bake, transfer your dough onto a sheet of parchment paper, place your dutch oven or combo cooker in the oven and preheat to 500 F.
Once the oven is hot, use oven mitts to pull the dutch oven out onto the stovetop. Take the lid off (HOT!) and transfer your dough into the dutch oven, taking care not to burn your wrists on the side of the "supernova hot" dutch oven sides. Using a very sharp knife (lame if you have one, or we find a tomato knife works great) make a series of artistic cuts on the surface of the dough, replace the lid on the dutch oven and place it back into the oven. Turn down the heat to 450 F.
Bake for 45 minutes, then remove the lid of the dutch oven and bake out for 15 minutes more.
Remove the dutch oven and turn out the bread to cool on a cooling rack. It will crackle satisfyingly as it cools. This is good.
Revel in your creation