Preparation

Mix the dough:

• The day before baking, mix the dough and let it spend the night in the refrigerator. Combine the flour, water, sugar, salt, and yeast in the large bowl of a stand mixer (use the paddle attachment, not the dough hook). Slowly mix until the ingredients form a ball around the paddle, about 30 seconds. Switch to the dough hook and mix on medium low for another 3 minutes. Stop the machine to scrape the dough off the hook; let the dough rest for 5 minutes and then mix on medium low for another 3 minutes, until it’s relatively smooth. At this point, the dough will resemble melted mozzarella and be very sticky. If you stretch a small piece, it will barely hold together.
• Coat a bowl large enough to hold the dough when it doubles in size with 1 Tbs. of the olive oil. Transfer the dough to the bowl and rotate the dough to coat it with the oil.
• Hold the bowl steady with one hand. Wet the other hand in water, grasp the dough and stretch it to nearly twice its size.
• Lay the stretched section back over the dough. Rotate the bowl a quarter turn and repeat this stretch-and-fold technique. Do this two more times so that you have rotated the bowl a full 360 degrees and stretched and folded the dough four times. Drizzle 1 Tbs. of the olive oil over the dough and flip it over. Wrap the bowl well with plastic and refrigerate it overnight, or for at least 8 to 10 hours.

Shape the focaccia:

• Remove the bowl of dough from the refrigerator and start shaping the focaccia 3 hours before you intend to bake it (2 hours on a warm day). The dough will have nearly doubled in size. Cover a 13×18-inch rimmed baking sheet with parchment or a silicone baking mat and coat the surface with 2 Tbs. of the olive oil.
• Gently slide a rubber spatula or a dough scraper under the dough and guide it out of the bowl onto the center of the pan. The dough will sink beneath its own weight, expelling some gas but retaining enough to keep an airy gluten network that will grow into nice holes.
• Drizzle 2 Tbs. of the olive oil on top of the dough. (Don’t worry if some rolls off onto the pan; it will all be absorbed eventually.)
• Dimple the entire dough surface, working from the center to the edges, pressing your fingertips straight down to create hollows in the dough while gently pushing the dough down and out toward the edges of the pan. At first you might only be able to spread the dough to cover about one-half to three-quarters of the pan. Don’t force the dough when it begins to resist you. Set it aside to rest for 20 minutes. The oil will prevent a crust from forming.
• After letting the dough rest, drizzle another 2 Tbs. olive oil over the dough’s surface and dimple again. This time, you will be able to push the dough to fill or almost fill the entire pan. It should be about 1/4 to 1/2 inch thick. If it doesn’t stay in the corners, don’t worry; the dough will fill the corners as it rises.
• Cover the dough loosely with oiled plastic wrap, put the pan on a rack to let air circulate around it, and let the dough rise at room temperature until it’s about 1-1/2 times its original size and swells to the rim of the pan. This will take 2 to 3 hours, depending on the temperature of the room. Thirty minutes before baking, heat your oven to 475°F.

Bake the focaccia:

• Just before baking, gently remove the plastic wrap and sprinkle a few pinches of sea salt or kosher salt over the dough. Put the pan in the middle of the hot oven and reduce the heat to 450°F. After 15 minutes, rotate the pan to ensure even baking.
• Check the dough after another 7 minutes. If it’s done, it will be golden brown on top and, if you lift a corner of the dough, the underside will be golden as well. If not, return the pan to the oven for another 1 to 2 minutes and check again.
• Set a cooling rack over a sheet of aluminum foil or parchment (to catch drippings). Use a metal spatula to release the dough from the sides of the pan. Slide the spatula under one end of the focaccia and jiggle it out of the pan onto the rack. If any oil remains in the pan, pour it evenly over the focaccia’s surface. Carefully remove the parchment or silicone liner from beneath the focaccia. Let cool for 20 minutes before cutting and serving.