Place the starter, salt, and water in a large bowl. Stir with a spatula to combine — it doesn’t have to be uniformly mixed. Add the flour. Mix again until the flour is completely incorporated.

If time permits, perform one 'fold': 30 minutes after you mix the dough, reach into the bowl and pull the dough up and into the center. Turn the bowl quarter turns and continue this pulling 8 to 10 times.

Drizzle with a splash of olive oil and rub to coat. Cover bowl with a tea towel or bowl cover and set aside to rise at room temperature (70ºF/21ºC) for 4 to 18 hours.

When dough has doubled, place 2 tablespoons of olive oil into a 9×13-inch pan. If you are using a glass pan, you may want to butter it first or use baking paper to prevent sticking.

Drizzle dough with a tablespoon of olive oil. 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 top of dough with oil. Leave alone for 4 to 6 hours, uncovered, or until puffy and nearly doubled.

Heat oven to 425ºF, 200C (fan oven). Rub hands lightly with oil, and using all ten fingers, press gently into the dough to dimple and stretch the dough to nearly fit the pan. Sprinkle generously with sea salt and rosemary. 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.