Directions

1. 1
   The night before: in a large bowl, whisk together the flour, salt and instant yeast. Add the cool water and stir with a wooden spoon until a sticky shaggy dough forms with no dry flour. Cover tightly with plastic wrap and refrigerate for 12-24 hours.
2. 2
   The next day, the dough will have roughly doubled and be full of bubbles. Generously oil a 23 x 33 cm baking pan, using a good 3 tablespoons of olive oil.
3. 3
   Scrape the dough directly into the pan. With oiled hands, gently stretch it out toward the corners. It won't want to fully cooperate; that's fine.
4. 4
   Cover loosely and let rise at room temperature for 1 1/2 to 2 hours, until puffy. It should now fill the pan.
5. 5
   Preheat the oven to 230 C (450 F) with a rack in the middle.
6. 6
   Drizzle the top of the dough with another 2 tablespoons olive oil. Dip your fingers in oil and press firmly straight down through the dough, creating deep dimples all over the surface.
7. 7
   Scatter the rosemary leaves on top and sprinkle generously with flaky salt.
8. 8
   Bake for 22-26 minutes until deeply golden on top and bottom. Slide a spatula underneath to check the bottom is crisp and brown.
9. 9
   Transfer to a rack and brush with another tablespoon of olive oil while hot. Let cool at least 15 minutes before slicing.