Combine Ingredients: In a large mixing bowl, combine the sourdough starter with the wheat flour and all-purpose flour. Gradually add the water, mixing until a rough dough forms.
Knead the Dough: Transfer the dough to a floured surface and knead it for about 10-15 minutes until it becomes smooth and elastic. The dough should be slightly tacky but not too sticky.
First Rise: Place the dough in an oiled bowl, cover it with a damp cloth, and let it rise for 4-6 hours at room temperature, or until it doubles in size.
Shape the Dough: Once the dough has risen, gently punch it down and transfer it to a floured surface. Shape it into a round or oval loaf, depending on your preference.
Second Rise: Place the shaped dough into a proofing basket or bowl, cover, and let it rise for another 2-3 hours, until the dough puffs up.
Preheat the Oven: Preheat your oven to 475°F (245°C) with a Dutch oven or baking stone inside for at least 30 minutes.
Bake the Bread: Carefully transfer the dough to the preheated Dutch oven or stone. Cover with a lid or baking dish and bake for 30 minutes. Then, remove the cover and continue baking for another 15-20 minutes, until the loaf is golden brown with a crisp crust.
Cool and Slice: Let the bread cool on a wire rack for at least 30 minutes before slicing to allow the flavors to fully develop.