In a large bowl, whisk together the sourdough starter and warm water until mostly dissolved.
Add the flour and mix until no dry bits remain. Cover and let rest for 30 minutes.
Sprinkle the salt over the dough and drizzle in the olive oil. Gently fold the dough until incorporated.
Cover and let the dough ferment at room temperature for 4–6 hours, performing 3–4 sets of stretch and folds during the first 2 hours, until puffy and roughly doubled.
(Optional) For deeper flavor, refrigerate the dough for 8–24 hours.
Generously oil a 9×13-inch baking dish or large cast iron skillet. Transfer the dough to the pan and gently stretch toward the edges. Rest 15 minutes if needed.
Cover and let rise for 2–4 hours, until jiggly and airy.
Preheat the oven to 425°F.
Drizzle the dough generously with olive oil. Use your fingertips to press deep dimples across the surface. Sprinkle with flaky sea salt and desired toppings.
Bake for 22–28 minutes, until golden brown with crisp edges.
Remove from the oven and drizzle with additional olive oil if desired. Cool slightly before slicing.