Using a stand mixer fitted with dough hook attachment, combine flour, sourdough starter, water, and salt on medium-low speed (or stirring by hand) until ball of doughforms that cleans sides of bowl, about 3 minutes.
Place dough into large, oiled mixing bowl and cover tightly with plastic wrap. Let rise in a warm spot in your kitchen until doubled in bulk, 8–12 hours.
Place a cast iron or enameled Dutch oven in oven, and heat to 450°.
Turn dough onto floured work surface and gently form into a boule. Cover with plastic wrap and allow to rise for 30 minutes.
Uncover your dough and re-form it, if necessary. Place your dough into pre-heated Dutch oven and cover with lid. Bake for 30 minutes, remove lid and continue baking until bread is browned, about 15 minutes.
Allow to cool completely before slicing and serving.