Combine 100 g of sourdough starter, 10 g of kosher salt, and 430 g of water in a bowl. Stir until salt dissolves, then add 512 g of bread flour. Mix until sticky dough forms.

Cover the bowl and let the dough rise at room temperature for 8–18 hours.

Drizzle a tablespoon of olive oil over the dough and gently deflate it by folding the edges towards the center.

Transfer to an oiled baking dish, stretch and dimple the dough, then cover and let it rise for 5-6 hours.

Preheat the oven to 425°F (220°C) and bake the focaccia for 25 minutes.

Let it cool in the pan for 10 minutes, then transfer to a wire rack.