The morning of the day before, prepare the pre-ferment: in a bowl, combine the flour and dry yeast. Gradually add the water and knead thoroughly for at least 10 minutes until you obtain a smooth, lump-free ball of dough. Dust a bowl with flour, place the dough ball inside, and score a cross on top. Cover and let it rise at room temperature for 2 hours, or until doubled in size. Then transfer it to the refrigerator and leave it until the following morning.
The next morning, remove the pre-ferment from the refrigerator and cut it into 6 small pieces. Place them in a mixing bowl and pour the lukewarm water over them. Let rest for 5 minutes.
Gradually add the 250 g of flour and knead thoroughly for another 10 minutes. Lightly flour your work surface, shape the dough into a ball, score a cross on top, and cover with a clean kitchen towel. Let it rise on the work surface for a generous hour.
Take the risen dough ball and gently shape it into an oblong loaf. Lightly oil a baking sheet and dust it with flour, then place the loaf in the center. Lightly dust the top of the loaf with flour and make a lengthwise slash with a sharp knife. Cover and let rise for an additional 45 to 60 minutes.
In the meantime, preheat the oven to 200 °C (400 °F). Place an aluminum or ceramic baking dish filled with water on the bottom rack of the oven to generate steam.
Once the dough has risen, place the loaf in the oven and bake for 20 to 30 minutes, until completely golden brown. You can insert a skewer or toothpick into the center to test for doneness.
Once baked, remove the bread from the oven and let it cool completely on a wire rack before serving.
