1. Prepare the Biga:
– In a bowl, mix flour, yeast, and water until combined into a shaggy dough.
– Cover with plastic wrap and let rest at room temperature for 12-16 hours until bubbly and doubled in size.

2. Mix the Ciabatta Dough:
– In a KitchenAid mixer bowl, add the biga, flour, salt, yeast, water, and olive oil.
– Mix on low speed for about 5 minutes until the ingredients are fully incorporated and form a very wet, sticky dough.
– Let the dough rest for 30 minutes to allow it to hydrate and begin developing structure.

3. Knead the Dough with Stretch-and-Fold Technique:
– On a well-floured surface, use the stretch-and-fold technique: gently stretch the dough, fold it over, rotate, and repeat.
– Perform a set of folds every 30 minutes for 2 hours to further develop the gluten, which will give the bread structure and an airy crumb.

4. First Rise:
– Place the dough in a lightly oiled bowl, cover, and let it rise for 1½ to 2 hours until doubled in size.

5. Shape the Loaves:
– Carefully turn the dough onto a floured surface. Divide it in half, shaping each into a rectangle, handling gently to keep bubbles intact.
– Place the shaped loaves on a parchment-lined baking sheet dusted with flour and semolina.

6. Second Rise (Proofing):
– Dust the tops with flour, cover with a cloth, and let the loaves rise for 30-45 minutes until puffy. This final proofing allows the dough to relax and achieve its airy structure.

7. Preheat and Bake:
– Preheat a cast iron pan in the oven to 250°C (475°F).
– Carefully remove the hot pan, dust with semolina, and place one loaf in the pan. Cover (if possible) to trap steam.
– Bake at 250°C (475°F) for 15 minutes with the lid, then uncover and bake for another 10-15 minutes until golden brown and crisp.

8. Cool:
– Transfer the ciabatta to a wire rack and let it cool completely before slicing to enjoy the full flavor and texture.