In a large bowl, combine the bread flour and water, mixing until no dry spots remain. Let this rest (autolyse) for 30 minutes to improve gluten development.

Add the active sourdough starter and salt to the dough. Mix thoroughly by hand using a stretch-and-fold method.

Let the dough rest in a covered bowl for 4 hours at room temperature, performing stretch-and-folds every 30 minutes. After the first hour, gently fold in the chopped olives and rosemary.

Turn the dough onto a lightly floured surface, shape it into a round or oval, and place it into a well-floured banneton basket or a bowl lined with a floured towel.

Cover and let the dough proof at room temperature for 1.5 hours, until slightly puffy but not over-proofed.

Preheat the oven to 475°F (245°C). Place a Dutch oven inside to heat for 30 minutes. Transfer the dough onto parchment paper, score the top, and carefully place it into the hot Dutch oven. Cover and bake for 20 minutes, then remove the lid and bake for another 25 minutes until golden brown.

Allow the loaf to cool for at least an hour before slicing to ensure the crumb sets properly.