In the bowl of a stand mixer fitted with a dough hook, combine starter, water, all-purpose flour, bread flour, and salt. Mix on medium speed for 3-5 minutes until dough pulls away from side of bowl and stays on hook. Cover and let rest 10 minutes to allow the water to absorb into the dough.

Turn mixer back on low speed, and very slowly drizzle in the olive oil. Return to medium speed for 2 minutes or until dough comes together (dough will be a bit lumpy/shaggy and quite wet.

Transfer dough to an oiled bowl and cover. Let rise for 2 hours, folding the dough over a few times every 30 minutes (this helps distribute the yeast).

Generously oil a 9x13” nonstick pan with olive oil. Transfer dough to the pan and stretch to cover the pan as much as possible, spreading/stretching every 30 minutes until dough covers the bottom of the pan. (Use wet or oiled hands for this.)

Cover and rise until doubled and very bubbly, about 4-6 hours depending on starter activity and ambient temperature.

Preheat oven to 425°F. Position rack in the lower third of the oven.

Drizzle top of dough generously with olive oil. Poke dimples all the way down to the bottom of the pan across the entire surface of the dough.

Sprinkle with flaky sea salt.

Bake 425°F for 25 minutes until golden. Let cool in pan for several minutes then transfer to a wire rack to cool.

Slice and enjoy.