1. 1. Combine Wet Ingredients and Starter: In a large mixing bowl, combine your active sourdough starter, warm water, granulated sugar, salt, and olive oil. Whisk everything together until the starter is mostly dissolved and the mixture is well combined. It should look milky and slightly bubbly from the starter.

2. 2. Add Flour and Mix the Dough: Gradually add the all-purpose flour to the wet ingredients, along with the optional instant yeast if you’re using it. Mix with a sturdy spoon or your hands until a shaggy dough forms. It doesn’t need to be perfectly smooth at this stage, just ensure all the flour is incorporated.

3. 3. Knead the Dough: Turn the dough out onto a lightly floured surface. Knead for 8-10 minutes until the dough becomes smooth, elastic, and passes the windowpane test (you should be able to stretch a small piece thin enough to see light through it without tearing). If the dough is too sticky, add a tiny bit more flour, but be careful not to add too much.

4. 4. First Rise (Bulk Fermentation): Lightly grease your mixing bowl with olive oil. Place the kneaded 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 4-8 hours, or until it has at least doubled in size. Alternatively, you can place it in the refrigerator overnight (8-12 hours) for a slower, more flavorful rise.

5. 5. Shape the Loaf: Gently punch down the risen dough to release the air. Turn it out onto a lightly floured surface. Shape the dough into a tight log that will fit comfortably into your loaf pan. To do this, flatten the dough into a rectangle, then fold the top third down to the center, and the bottom third up over that. Pinch the seam closed, then roll the dough into a cylinder, tucking the ends under to create tension on the surface.

6. 6. Second Rise (Proofing): Lightly grease a 9×5-inch loaf pan. Place the shaped dough into the prepared pan. Cover loosely with plastic wrap or a damp towel and let it rise in a warm spot for 1-2 hours, or until it has nearly doubled in size and looks puffy. It should just crest over the top of the loaf pan.

7. 7. Preheat Oven and Bake: While the dough is on its second rise, preheat your oven to 375 F (190 C). Once the dough has risen sufficiently, place the loaf pan in the preheated oven. Bake for 35-40 minutes, or until the crust is golden brown and the internal temperature reaches 200-210 F (93-99 C) when measured with an instant-read thermometer.

8. 8. Cool Completely: Remove the bread from the oven and immediately turn it out onto a wire rack. Allow the loaf to cool completely for at least 1-2 hours before slicing. Slicing too early can result in a gummy texture.