In a large bowl, combine 500g bread flour (Or all purpose flour works well) and 350g water. Stir until no dry flour remains. Cover and let it rest for 30 minutes (autolyse).
Add 100g of active starter and 10g salt. Mix until well incorporated. (It will look like a shaggy ball of dough)
Stretch and Fold: **This is an optional step. You can stretch and fold your dough, or, let it sit and rise without stretching and folding. Although this is optional, this step will add height and texture to your homemade sourdough bread, and... it's fun to do! Over the next 4 hours, perform 4 sets of stretch-and-folds every 30 minutes. To do this, grab one side of the dough, stretch it upward, and fold it over itself. Rotate the bowl and repeat. (If I am honest, there are times I do NOT get to this... if I leave my bread in the bowl and do not stretch and fold, it is still just as yummy!)
Rest: Let the dough rest, and let the dough rise covered, for the remainder of the bulk fermentation. By the end, it should have a smooth side, be bubbly, and slightly jiggly. This bulk fermentation can take anywhere from 4-12 hours. It all depends on the temperature of your kitchen. The warmer the environment, the less time it takes to rise. My advice is to watch your dough and not the clock! Once your dough has doubled in size, it is ready to shape.
Flatten: Lightly flour your work surface. Turn out the dough and gently shape it into a rectangle shape by pulling the sides and edges out.
Shape: Fold over the long edges to meet in the middle then roll into a ball. Place it seam-side up in a floured banneton or mixing bowl, lightly floured.
Room Temperature: Proof the dough at room temperature for 1-2 hours.
Cold Fermentation: Transfer the dough to the fridge to ferment for at least 3 hours, up to 12 hours. This step enhances the flavor and makes the dough easier to handle.
Preheat the Oven: Place your Dutch oven inside your oven and preheat to 450°F (245°C) for at least 30 minutes- I usually place mine in while it preheats and that works perfectly.
Score the Dough: Remove the dough from the fridge. Turn it out onto a sheet of parchment paper and use a lame, razor blade or sharp knife to score the top.
Bake: Carefully place dough in the hot Dutch oven while on the parchment paper. Cover and bake for 40 minutes. If you like a darker crust, remove lid and bake for another 5-8 minutes.
Cool: Let the bread cool on a wire rack for at least 1 hour before slicing.