1. Activate Your Starter: In a large mixing bowl, combine the active sourdough starter with the warm water and honey (or maple syrup). Stir gently until the starter is mostly dissolved and the mixture is cloudy. It should look milky and slightly frothy, indicating your starter is alive and ready.

2. Combine Dry Ingredients: Add the salt, all-purpose flour, oat bran, and whole wheat flour to the wet ingredients in the bowl. Mix with a sturdy spoon or your hands until a shaggy dough forms. Don’t worry if it looks a bit rough; it will smooth out.

3. Knead the Dough: Turn the dough out onto a lightly floured surface. Knead for 5-7 minutes. If the dough is sticky, lightly oil your hands instead of adding too much flour, which can make the bread dense. You’re looking for a dough that is still slightly tacky but smooth and elastic.

4. First Rise (Bulk Fermentation): Lightly grease a clean bowl with olive oil. Place the dough in the bowl, turning it once to coat all sides with oil. Cover the bowl with plastic wrap or a damp kitchen towel. Let it rise in a warm spot for 4-6 hours, or until it has nearly doubled in size. Alternatively, you can place it in the refrigerator for 8-12 hours for a slower, more flavorful rise. The dough should look puffy and have some visible bubbles.

5. Shape the Loaf: Gently turn the risen dough out onto a lightly floured surface. Gently deflate it by pressing down lightly. Shape the dough into a round or oval loaf. You can do this by folding the edges towards the center and then flipping it over, using the surface tension to create a smooth top.

6. Second Rise (Proofing): Place the shaped loaf into a floured banneton basket or a bowl lined with a floured kitchen towel. Cover loosely with plastic wrap or a damp towel. Let it rise for 1-2 hours at room temperature, or until visibly puffy and springs back slowly when gently poked.

7. Preheat and Score: About 30 minutes before baking, preheat your oven to 450 F (230 C) with a Dutch oven or baking stone inside. Carefully remove the hot Dutch oven. Gently transfer the proofed dough into the hot Dutch oven (or onto the baking stone). Using a sharp knife or a bread lame, score the top of the loaf with a few shallow cuts. This helps the bread expand evenly.

8. Bake the Loaf: Cover the Dutch oven and bake for 30 minutes. Remove the lid and continue baking for another 10-15 minutes, or until the crust is deep golden brown and the internal temperature reaches 200-210 F (93-99 C).

9. Cool Completely: Carefully remove the bread from the Dutch oven and transfer it to a wire rack. Let it cool completely for at least 1-2 hours before slicing. This step is crucial for the crumb to set and for the best texture and flavor.