Mix sourdough starter and water in a large glass or ceramic bowl. Add flour and salt, then mix to form a shaggy dough. Cover and rest for 1 hour.

After autolyse, stretch and fold the dough from the edges toward the center until a smooth ball forms. Cover and rest for 30 minutes.

Perform 4 to 6 sets of stretch and folds, 15 minutes apart. Stretch dough up and fold over itself 4 times per set.

Cover dough and ferment until risen just under double in size. Time depends on room temperature.

Turn dough onto counter, divide into 175–200g portions. Preshape into rounds, rest 30 minutes. Shape into baguettes using stretch, fold, and tension technique. Place into floured couche or cloth.

Let shaped baguettes rest at room temperature for about 2 hours, depending on ambient temperature.

Cover baguettes and refrigerate for 12–18 hours, or up to 36 hours for deeper flavor.

Preheat oven to 230°C/450°F with cast iron bread pan inside. Preheat for 1 hour if possible.

Remove baguettes from fridge, place on parchment. Score with a lame or razor. Bake 15 minutes with lid on at 230°C/450°F, then 10–15 minutes with lid off at 210°C/410°F.

Remove baguettes from the pan and cool on wire rack before slicing.