Mix the bread flour and water together until no dry flour remains. Rest 1 hour (autolyse).

Add the starter and mix in, then add the salt and work by hand until fully incorporated.

Bulk ferment: do 2 sets of stretch-and-folds, then 2 sets of coil folds, 30 minutes apart.

Continue bulk fermentation until the dough is well aerated and risen 30-50%, about 4 hours depending on kitchen temperature.

Shape into a round or batard and place seam-side up in a floured banneton.

Cover and refrigerate overnight to cold proof.

Bake at 250°C for 25 minutes with steam, then 230°C for 20-25 minutes without steam, until deeply golden.

Cool completely before slicing.