In a large bowl combine the flour, yeast, salt, and rosemary. Add the water and olive oil and stir with a large spoon until the flour is completely incorporated. You may need to get your hands in there to finish mixing in the flour. The dough will be wet and sticky. Cover the bowl with plastic wrap and let it sit in a warm spot in the kitchen for 10-12 hours.
Once the dough is covered in bubbles and looks puffy the dough is ready to be shaped.
Lightly dust a work surface with flour and sprinkle a little more flour over the top of the dough. Using your fingertips, scrape the dough out of the bowl onto the floured surface. Fold over the dough a few times to give the dough a little structure. Then gather the dough into a ball. Brush a piece of parchment paper with oil. Put the dough onto the parchment and cover it with a damp kitchen towel. Let the dough rest for 1 hour.
30 minutes before you are going to bake the bread, put a large (oven safe) pot with a lid into the oven and heat the oven to 500F.
When you are ready to bake, you can either cut a slit in the top of the bread with a serrated knife or grease another piece of parchment and flip the bread onto the new piece so that the seam side of the bread is facing up. Either will let the bread expand during baking.
Then pick up the bread by the corners of the parchment and lower it into the large pot. Cover the pot and put it back in the oven. Lower the heat to 425F. Bake the bread for 30 minutes.
Remove the lid and bake for an additional 15 minutes. Transfer the bread to a rack and let cool.