Prepare your sourdough starter by mixing together 1/2 cup of starter, 1/2 cup flour and 1/2 cup of water in a large liquid measuring cup. Let the mixture grow for 6-12 hours. It is ready to use when it is bubbly and growing.
When the starter is ready, stir together the starter and 1 1/4 cup of water in a large mixing bowl. Mix until the starter is fully dissolved into the water; I like using a dough hook or my hands.
Add 3 cups of flour and mix until fully incorporated. There should be no dry spots and the dough should be sticky.
Cover the dough with plastic or a clean dish towel and let it sit for 30 minutes.
Add 2 teaspoons of salt and 2Tablespoons of rosemary to the dough. Take a section of the dough and stretch it and place it down into the middle of the dough. Take the adjacent section and pull it and place it down in the center. Continue stretching around the entire circumference of the dough until the salt and rosemary are incorporated and can no longer be felt in the dough.
Cover the dough and let it sit for 30 minutes.
With wet hands, stretch and fold the dough again. Go around the circumference of the dough twice.
Cover the dough and let it sit for 30 minutes.
With wet hands, stretch and fold the dough again. Go around the circumference of the dough twice.
Cover the dough and let it sit for 30 minutes.
With wet hands, stretch and fold the dough again. Go around the circumference of the dough twice.
Cover the dough and let it sit for 2 1/2 hours.
Remove the dough from the bowl onto a lightly floured surface and stretch and fold the dough around the edges onetime. Flip the dough over onto the smooth side and with the tips of your fingers touching, pull the dough towards you to tighten the loaf. Turn the dough a quarter turn and pull towards you again. Turn and pull again until the entire circumference has been pulled towards you.
Leave the dough on the counter and cover it with a clean dish towel and let it rest for 30 minutes. The dough should hold it's shape and not fall flat. If it becomes flat (like a pancake), repeat the previous step until it holds it's shape.
Flip the dough over, smooth side down onto the counter, stretch and fold the dough around the edges. Flip the dough so the smooth side is up and with the tips of your fingers touching and your pinkies touching the counter, pull the dough towards you to tighten the loaf. Turn the dough quarter turns until you've pulled in the dough around the entire area. It should be a tight ball shape.
Place the dough, smooth side down, into a banneton proofing basket or parchment lined mixing bowl. Cover and let it rise for 60-90 minutes.
Place the basket/bowl covered in the refrigerator for at least 3 hours.
Turn the dough carefully onto parchment paper and score the dough.
Preheat the oven to 450 degrees F with a dutch oven inside. Carefully remove the lid to the dutch oven and place the loaf inside with the parchment paper. Place the lid back on and bake for 25 minutes. Remove the lid and bake an additional 10-20 minutes, or until it has browned to your liking.
Remove the loaf from the dutch oven and place it on a cooling rack. Brush the top of the loaf with 1 Tablespoon olive oil. Sprinkle 1 teaspoon of rosemary and 1 teaspoon of coarse salt. Let the loaf cool completely.