To make the biga: Stir the water, flour, and yeast together, cover, and let rest at room temperature for 12 to 16 hours., To make the dough: Add the water to the biga, mixing to incorporate the two. Combine the flour, yeast, and salt in a separate bowl, and add to the biga-water mixture. Mix on low speed of a stand mixer fitted with a dough hook until the dough becomes cohesive, about 2 minutes. Increase the mixer to medium speed and knead to form an elastic, sticky dough, about 3 to 4 minutes. Resist the urge to add more flour unless the dough is truly "soupy.", Cover the dough in the bowl, let it rise for 1 hour, then gently deflate it. Let it rise another hour, then turn it out onto a liberally floured work surface, and sprinkle lots of flour on top., Flatten the dough to an 8" x 10" rectangle and cut it into two pieces, each 4" x 10"., Transfer the loaves onto a piece of parchment, leaving about 6" between them. Cover with a lightly greased piece of plastic wrap or a freestanding plastic cover, and let rise until they're very puffy, 1 1/2 to 2 hours., About 30 minutes before the loaves are ready to bake, preheat the oven to 500°F. If you have a baking stone, place it in the middle of the oven when you start preheating, so it gets nice and hot. , Spritz the dough with water; or add steam to your oven (see "tips," below). If you're baking on a stone, transfer the bread to the stone, parchment and all. If you're using a pan, transfer the loaves on their parchment to a baking sheet, and place them on a middle rack of the oven. Lower the oven temperature to 425°F., Bake the ciabatta until it's golden brown, approximately 22 to 25 minutes. Turn the oven off, place ciabatta on the oven's middle rack (remove the stone if you’ve used one), crack the door open about 2", and allow ciabatta to cool completely in the turned-off oven.  , Fresh ciabatta is best enjoyed within a couple of days. For longer storage, wrap well and freeze.