In a large bowl combine the water and starter.  Stir together so the water turns a milky color.

Add the flours and sprinkle the salt on top of the flour.  Stir everything together first with a wooden spoon and then with your hands.  The dough will be pretty wet.  Cover the tough and leave at room temperature for 8-10 hours for bulk fermentation.  If you have the time, give the dough a couple of turns in the first hour or two.  If you don’t have the time, no worries, it will still make a great loaf.

After bulk fermentation, turn the dough out on a floured surface.  Let it rest for 10 minutes.

Oil a 9×13” pan.  Shape the dough into a ball and place it in the pan.  Rub the surface with olive oil.  Cover with plastic wrap and refrigerate for 8-12 hours.

Remove the dough from the fridge and let it sit at room temperature for 30-60 minutes.  Preheat the oven to 500 F.

Stretch the dough as needed to reach the corners of the pan.  Use your fingertips to press down on the surface to help stretch the dough and leave little divots all over the surface.  Sprinkle the dough with flake sea salt (I use Maldon).

Bake for 15-20 minutes.  When it’s done, it will have pulled away from the sides of the pan.  Remove it from oven.  As soon as it is cool enough to work with, remove it from the pan and finish cooling on a wire rack.