Mix the Dough: In a large bowl, combine the sourdough starter, water, and olive oil. Stir until the mixture looks milky. Add the flour and salt, then mix until there are no dry flour clumps. Cover the bowl and let the dough rest for 1 hour.

Stretch and Fold: Focaccia dough is flexible, but it benefits from a couple of stretch-and-folds. Perform 1-2 sets of stretch-and-folds, spaced 30 minutes apart.

Bulk Fermentation: Allow the dough to bulk ferment at room temperature for 8-10 hours or overnight, until it has doubled in size.

Shape and Proof: Once bulk fermentation is complete, transfer the dough into a greased 9x13 baking dish. Gently fold both sides of the dough toward the middle and flip it upside down in the pan. Let it rest for an additional 1-2 hours to allow the dough to relax and spread out in the pan.

Add Toppings and Dimple: Preheat the oven to 425°F (220°C). Drizzle the top of the dough generously with olive oil, then sprinkle your chosen seasonings or herbs on top. Using both hands, press your fingers into the dough to create deep dimples across the surface.

Bake: Bake the focaccia for about 30 minutes, or until it reaches an internal temperature of 205°F (96°C) and has a golden, crispy crust.

Cool and Serve: Remove the focaccia from the oven, let it cool slightly, and transfer it out of the pan. Top with flaky sea salt, slice, and enjoy!