Place the starter, salt, and water in a large bowl. Whisk to combine.

Add the flour and mix until it is completely incorporated. Cover with cling wrap and a kitchen towel and rest for 30 minutes at room temperature.

After 30 minutes, reach into the bowl and pull the dough up and into the center. Turn the bowl quarter turns and continue this pulling 8 times. This method of stretching and folding strengthens the dough and builds those big bubbles so don't skip it.

Add a drizzle of olive oil to the bowl and swirl around the dough to coat. Cover bowl with cling wrap and a kitchen towel and set aside to rise at room temperature overnight, roughly 12-18 hours.

When dough has doubled, generously pour 2 tablespoons of olive oil into a 9×13-inch pan.

Use your hand to gently deflate the dough and release it from the sides of the bowl. Gently scoop the dough into the center of the pool of oil in your prepared pan. Fold dough envelope style from top to bottom and side to side to create a rough rectangle. Turn dough over so seam-side is down.

Rub the top of the dough with the remaining 1 tablespoon of olive oil. Leave alone for 4-6 hours or until bubbly and nearly doubled.

Preheat oven to 425ºF (210°C). Rub fingers lightly with oil and press gently into the dough to dimple and stretch the dough over and over again. Push the dough until it is reaching the sides of the pan. Sprinkle generously with tomatoes, olives, rosemary, and sea salt.

Transfer pan to the oven and bake for about 25 minutes or until golden all around. Remove pan from oven and transfer bread to a cooling rack. Cool at least 20 minutes before slicing.

Store at room temperature for up to 3 days. It also freezes very well.