Whisk flour, yeast, and salt in a large bowl until combined.
Stir in water with wooden spoon until sticky, shaggy dough forms with no dry flour.
Cover tightly with plastic wrap; rest at room temperature 12 to 18 hours until surface bubbles and dough more than doubles.
Turn onto generously floured surface; dust top with flour.
Gently shape rectangle; halve into two loaves.
Transfer to parchment-lined baking sheet; cover loosely with kitchen towel and rest 1 hour.
Preheat oven to 425°F; place metal pan on bottom rack.
Just before baking, add 1 cup hot water to metal pan for steam; immediately put bread in oven.
Bake 40 to 45 minutes until deep golden brown and hollow-sounding when bottom tapped; cool on wire rack at least 30 minutes before slicing.