In a large bowl or the bowl of a stand mixer, whisk the yeast into the water and let sit 5 minutes.
Add 3 cups flour and the salt and mix, using the paddle attachment, until just combined.
Switch to the dough hook and knead on low speed for about 5 minutes, or until dough is elastic (or remove dough from bowl and knead by hand for 15 minutes). Shape dough into a ball and place in a greased bowl, cover with plastic wrap or damp tea towel, and let rise at room temperature until it has doubled, about 3 hours.
Punch down the risen dough and divide into two pieces. Roll each piece into a 1/2-inch-thick, foot-long rectangle and place about 4 inches apart on a baking sheet lined with lightly-floured parchment paper. Cover with lightly greased plastic wrap and let rise for about 30 minutes.
Preheat oven to 400° F for 15 minutes.
Remove the plastic wrap and, with a sharp knife, make 3 or 4 diagonal slits in the dough.
Place in the oven, reduce heat to 375° F, and bake until golden brown, about 30 minutes.
Remove the bread and place on a cooling rack for 30 minutes.
Store the ciabatta wrapped in brown or parchment paper in a cool, dark place.