Mix together flour, starter, and water in a large bowl. I like to use my glass kitchen aid mixer bowl with the dough hook attachment. This makes for easy mixing in the beginning. First, I mix until all of the ingredients are incorporated. If the dough seems dry, it will moisten as it ferments. Cover the bowl and let sit for one hour.
To begin, add 1 tsp of salt and do a series of stretches and folds with the dough until the salt is well incorporated. It’s probably about 10 stretches and folds. I do this right in the mixing bowl. Cover the bowl and let sit for 1 hour.
Do another series of stretches and folds, around 5 or 6, and finish with the dough in a taught ball shape. I do this right in the mixing bowl. Cover and let sit for 1 hour.
Remove the dough from the bowl with a dough scraper onto a lightly floured surface. After that, perform another series of 5 or 6 stretches and folds.
Gently shape the dough into a rectangular shape, approximately 12 inches by 8 inches. Sprinkle with finely chopped fresh rosemary and Pecorino Romano.
Gently kneed the dough to fully incorporate the ingredients.
Form the dough into a taught ball with the seams on the bottom of the ball. Place formed dough into parchment lined bowl or bread baneton. Cover and set in a warm place to allow to rise for 1 hour. Preheat the oven to 450F. Often, I like to set my dough on the stove top while the oven and dutch oven are preheating .
Sprinkle the top of the loaf with the remaining Pecorino Romano cheese, veru slightly pressing it into the dough, but not changing the shape of the loaf.
With a sharp knife or bread lame, make a center cut at a 30-degree angle on the top of the bread. This will allow the bread to rise in a more uniform loaf shape. Remove the hot dutch oven and lift up the parchment paper with the dough in it and set it in the dutch oven. Place the lid on the dutch oven and put in the oven for 25 minutes. After that, remove the lid and bake for another 5 or so minutes until you have achieved the desired brownness of the loaf.
Your sourdough loaf is now ready to enjoy!