In a mixing bowl, combine the flour and water. Mix until no dry flour remains. Cover and rest for 30 minutes.
Add the sourdough starter and salt. Mix until fully incorporated.
Cover and let the dough rest for 4–5 hours, performing stretch-and-folds every 30 minutes during the first 2 hours.
Divide the dough into 4 equal pieces and shape each into a tight round boule.
Place the boules on parchment paper, cover, and proof for 1–2 hours until slightly puffy.
Preheat the oven to 450°F (230°C).
Score the tops of the boules with a sharp knife.
Bake for 22–25 minutes until golden brown and crusty.
Cool on a wire rack before slicing.