Make the Biga (Day 1):
In a bowl, mix flour, water, and yeast until combined.
Cover and let sit at room temperature for 12–24 hours until bubbly and slightly domed.
Prepare the Dough (Day 2):
Mix biga, flour, yeast, warm water, and salt in a large bowl.
Stir until a sticky dough forms (don’t knead).
Cover and let rest for 30 minutes.
Stretch and Fold:
Gently stretch and fold the dough every 30 minutes, repeating four times.
Cover and refrigerate for 1 hour to improve structure.
Shaping the Ciabatta:
Turn dough onto a floured surface.
Shape into a 10x7-inch rectangle without deflating air pockets.
Cut into 2 loaves or 8 rolls.
Place onto parchment paper and let rest for 1 hour.
Baking:
Preheat oven to 450°F (232°C). Place a tray of ice cubes or water in the oven for steam.
Bake for 20–25 minutes until golden brown.
Cool for 45 minutes before slicing.