Mix all the dry ingredients, then add the warm water and mix with a wooden spoon until a wet, sticky dough forms.
Cover the bowl with plastic wrap and set in a warm place for 8-18 hours. (It would work well to mix up in the morning before leaving for work). When it’s ready it will have risen, be flat on top, and have lots of bubbles visible.
Pre-heat oven to 450 F and place a 6 qt Dutch Oven inside.
Flour hands, punch down the dough. Dump it out onto a floured square of parchment paper. Shape into a ball, dust with flour. Cover with a piece of plastic wrap and let it rest for 30 minutes while the Dutch Oven pre-heats in the oven.
Carefully lift the parchment paper and set the dough in the Dutch oven. Cover and bake for 45 minutes. Then bake an additional 10 minutes without the lid until the top is golden.