1. Activate the Yeast and Starter: In a large mixing bowl, combine the warm water, active sourdough starter, and active dry yeast. Stir gently with a whisk or fork until the starter and yeast are mostly dissolved. Let this mixture sit for 5-10 minutes until it looks slightly foamy, indicating the yeast is active.

2. Combine Dry Ingredients: Add the all-purpose flour and fine sea salt to the wet mixture in the bowl. Use a wooden spoon or your hands to mix until all the flour is incorporated and a shaggy dough forms. It will be sticky, but don’t worry about kneading it perfectly at this stage.

3. First Rise (Bulk Fermentation): Drizzle 1 tablespoon of olive oil over the dough, cover the bowl with a clean kitchen towel or plastic wrap, and let it rest in a warm spot for 1 hour. During this time, the gluten will start to develop.

4. Stretch and Folds (Optional but Recommended): After 1 hour, perform a set of “stretch and folds.” With wet hands, gently grab a portion of the dough from the edge, stretch it upwards, and fold it over the center. Rotate the bowl and repeat this process 3-4 times. This helps build strength in the dough. Re-cover and let it rise for another 1-2 hours, or until it has noticeably increased in volume and looks bubbly. The total proofing time should be 2-3 hours.

5. Prepare for Baking: Generously drizzle 2-3 tablespoons of olive oil into a 9×13 inch baking pan or a 10-inch round cast iron skillet. Gently transfer the dough into the prepared pan, trying not to deflate it too much. Drizzle a little more olive oil over the top of the dough.

6. Dimpling and Topping: With oiled fingertips, gently press down into the dough, creating those characteristic focaccia dimples. Try to press all the way down to the bottom of the pan without tearing the dough. If desired, sprinkle with flaky sea salt and fresh rosemary or other herbs.

7. Bake to Golden Perfection: Preheat your oven to 425 F (220 C). Bake the focaccia for 20-25 minutes, or until it’s golden brown on top and sounds hollow when tapped on the bottom.

8. Cool and Serve: Once baked, carefully remove the focaccia from the pan and place it on a wire rack to cool slightly. This prevents the bottom from getting soggy. Slice into generous “sandwich slabs” or tear into pieces and enjoy warm.