1. 1. Prepare Your Starter and Mix the Dough: In a large mixing bowl, combine the active sourdough starter with the warm water. Stir gently until the starter is mostly dissolved. Add the salt, bread flour, whole wheat flour, rolled oats, flax seeds, sunflower seeds, and optional honey or maple syrup. Mix with a sturdy spoon or your hands until all the flour is hydrated and no dry spots remain. The dough will be shaggy. Cover the bowl with a damp cloth or plastic wrap and let it rest for 30 minutes (this is called autolyse, which helps with gluten development).

2. 2. Perform the First Set of Stretch and Folds: After the rest, uncover the dough. With damp hands, grab a portion of the dough from one side, stretch it upwards, and fold it over to the opposite side of the bowl. Rotate the bowl a quarter turn and repeat this process three more times, effectively folding all four sides. This helps build strength in the dough. Cover and let it rest for another 30 minutes.

3. 3. Continue with More Stretch and Folds: Repeat the stretch and fold process (Step 2) three more times, with 30-minute rest periods in between each set. You should complete a total of four sets of stretch and folds over a 2-hour period. You’ll notice the dough becoming smoother, more elastic, and holding its shape better with each set.

4. 4. Bulk Fermentation (First Rise): After the final set of stretch and folds, cover the bowl and let the dough rise at room temperature for 2-4 hours. The exact time will depend on the warmth of your kitchen and the activity of your starter. The dough should look visibly puffy and have increased in volume by about 30-50%. You should see some bubbles on the surface.

5. 5. Shape the Dough and Cold Proof: Gently turn the dough out onto a lightly floured surface. Shape it into a round or oval loaf. You can do this by gently pulling the edges of the dough towards the center and then flipping it over, using the surface tension to create a taut skin. Place the shaped dough seam-side up into a floured banneton basket or a bowl lined with a floured kitchen towel. Cover with plastic wrap and refrigerate for 8-12 hours, or up to 24 hours. This cold proof develops flavor and makes the dough easier to handle.

6. 6. Preheat Oven and Dutch Oven: About 45 minutes before you’re ready to bake, place your Dutch oven (with its lid) into your oven and preheat it to 450 F (230 C). This ensures the Dutch oven is scorching hot, which is crucial for a good crust.

7. 7. Score and Bake Your Bread: Carefully remove the hot Dutch oven from the oven. Gently invert the cold dough from the banneton into the hot Dutch oven. Using a sharp knife or a bread lame, score the top of the dough with a design of your choice (a simple cross or a single slash works well). This allows the bread to expand during baking. Place the lid back on the Dutch oven and bake for 30 minutes.

8. 8. Finish Baking and Cool: After 30 minutes, remove the lid from the Dutch oven. Reduce the oven temperature to 425 F (220 C) and continue baking for another 10-15 minutes, or until the crust is a deep golden brown and sounds hollow when tapped on the bottom. Carefully remove the bread from the Dutch oven and transfer it to a wire rack to cool completely for at least 1-2 hours before slicing. Slicing too early can result in a gummy texture.