In a small bowl or measuring cup, whisk together 1 3/4 cups warm water (90–100°F) and 1/2 tsp molasses until the molasses is dissolved.

In a large mixing bowl, whisk together 2 1/3 cups unbleached bread flour (290 g), 2 1/2 cups unbleached all-purpose flour (315 g), 1 1/4 tsp instant yeast, and 2 tsp salt until evenly combined.

Pour the water–molasses mixture into the dry ingredients. Mix with a wooden spoon, spatula, or low speed of a stand mixer until the ingredients come together into a single mass of dough.

Knead the dough for 4 minutes using a dough hook on low speed or by hand on a lightly floured surface. The dough should be soft and slightly sticky but should not cling to clean, dry fingertips. If the dough is excessively sticky after kneading, add more all-purpose flour 1 tablespoon at a time until manageable.

Lightly oil or dust a large bowl, place the dough inside, and cover loosely with plastic wrap. Let the dough rise at room temperature (about 69–75°F) for 4 hours.

During that 4-hour rest, perform a set of folds every hour (three times total): wet one hand with water to prevent sticking, gently punch the dough down, then fold the dough over itself a few times. Re-cover after each fold.

After the 4-hour bulk rise, shape the dough by drawing the edges into the center, then turn the dough over so the seam is on the bottom. Place the shaped dough seam-side down in a large bowl well dusted with all-purpose flour. Lightly sprinkle the top of the dough with flour, cover with a tea towel, and let rise at room temperature for 1 1/2 hours.

About 45–60 minutes into the final rise, place a pizza stone or an inverted heavy baking sheet on the center oven rack and a cast-iron pan on the bottom rack. Preheat the oven to 500°F with both pieces inside until fully heated.

When the dough has finished the final rise, prepare a work surface or the back of a baking sheet by dusting it generously with semolina flour (you may also use a little all-purpose flour as needed to prevent sticking). Invert the risen dough onto the semolina-dusted surface so the top (seam-side down) becomes the bottom.

Using a sharp knife or lame, score the top of the dough several times (long slashes about 1/4–1/2 inch deep) to allow controlled expansion during baking.

Slide the dough onto the preheated pizza stone or inverted baking sheet in the oven. (Use the semolina-dusted baking sheet or a peel to transfer the dough if needed.)

Bake at 500°F for 10 minutes, then reduce the oven temperature to 400°F and continue baking for 30–35 minutes, or until the crust is a deep golden brown.

Turn off the oven, crack the oven door open (use a wooden spoon or oven mitt to hold it slightly ajar), and leave the bread inside for 10 minutes to finish gently.

Remove the bread from the oven and transfer it to a wire rack. Let it cool for at least 15 minutes before cutting.