Loosen 500 grams poolish (1:1 flour to water, at or near peak) in 140 grams water, lukewarm (hold back 20 g), keeping 20 g of the water back. Add 250 grams bread flour and 1 grams instant yeast and mix until no dry flour remains. The dough will be shaggy and sticky.

Cover and rest so the flour fully hydrates.

Sprinkle 10 grams fine salt over the dough with the reserved 20 g of water. Squeeze and pinch it through until fully absorbed, then slap-and-fold or knead in the bowl for 3 to 5 minutes until the dough starts to pull away from the sides.

Bulk ferment at about 24°C (75°F) for roughly 2 to 2.5 hours. Do a set of coil folds with wet hands every 30 minutes for the first 1.5 to 2 hours (3 to 4 sets), then leave it alone. It's ready when it has grown about 50 to 75%, feels airy, and shows large bubbles along the sides and surface.

Dust the counter heavily with 30 grams flour or semolina, for dusting. Tip the dough out without degassing it and dust the top. Cut it into rectangles, one per loaf. Letter-fold each one loosely in thirds, then set it seam-side down on a floured couche or parchment. Handle the dough as little as possible.

Cover and proof until the dough looks puffy and a floured finger poke springs back slowly. Meanwhile, preheat the oven to 250°C (482°F) with a baking steel or stone if you have one.

Flip each loaf onto parchment so the seam faces up, which gives the rustic cracks, and gently stretch it to length. Load the loaves and bake at 250°C (482°F) with high steam.

Turn the steam off, vent it, and drop the oven to 230°C (446°F). Bake until the crust is deep brown and the internal temperature reaches 96 to 98°C (205 to 208°F).

Cool on a rack for at least 45 minutes before cutting, since the crumb is still setting.