Step 1 With a large metal spoon, stir together the flour, salt, yeast and water in a 4-quart bowl or the bowl of an electric mixer until combined.
Step 2 If using a mixer, fit it with the paddle attachment and mix on low speed until all the ingredients are hydrated and begin to form a wet ball of dough, about 2 minutes. Set the dough aside to rest for 5 minutes. Switch to the dough hook, add one-fourth cup olive oil and resume mixing on medium-low speed until all of the oil is incorporated and the dough is sticky, supple and smooth; it should clear the sides of the bowl and stick just a little to the bottom. This will take 3 to 4 minutes. If the dough seems like a batter and does not have sufficient structure to hold itself together, mix in more flour by the tablespoonful.
Step 3If mixing by hand, repeatedly dip one of your hands or the spoon into cold water and use it much like a dough hook, working the dough vigorously as you rotate the bowl with your other hand. As all the flour is incorporated and the dough becomes a wet ball, after about 3 minutes, stop mixing and set the dough aside to rest for 5 minutes. Then add the olive oil, dip your hand or spoon again in the water and continue to work the dough for 3 to 4 more minutes. The dough should be very sticky, but it should also have some texture and structure. If the dough seems like a batter and does not have sufficient structure to hold itself together, mix in more flour by the tablespoonful.
Step 4Form the dough into a ball and place it in a bowl brushed with olive oil. Turn the dough to coat it with the oil, cover the bowl with plastic wrap and immediately refrigerate it overnight. The next day the dough should have nearly doubled in size. Allow it to come to room temperature, about 2 hours, before making the focaccia.
Step 5To bake, line a 12-by-17-inch jellyroll pan with parchment or a silicone liner and oil well. Wet your hands and gently scrape the dough from the bowl onto the pan; be gentle with the dough to deflate it as little as possible.
Step 6Using only your fingertips, press down on the dough, creating dimples and pockets all over the surface. Do not press the dough outward toward the edges of the pan; instead, simply press downward at only a slight angle toward the edges. The dough will spread on its own; any attempt to force it toward the pan edges will tear it and cause uneven sections. The dough will probably fill the pan a little more than half full before it begins to become elastic and spring back toward the center. When this occurs, stop pressing, cover loosely with a damp cloth or plastic wrap, and set aside for the dough to relax at room temperature, about 15 minutes.
Step 7Repeat the dimpling process, beginning at the center and gradually working out toward the edges of the pan. This time the dough will nearly fill the pan. Try to keep the dough somewhat even across the top. Again, cover and set the dough aside to r