In a large bowl, whisk together the flour, salt, and yeast. Add the warm water to the flour mixture and stir with a wooden spoon until all the flour is incorporated and a sticky dough forms—no kneading required. Pour the 1/4 cup olive oil into a 6-quart plastic food container with a tight-fitting lid (or a large bowl). Transfer the focaccia dough to the plastic container, turn to coat, and cover tightly. (If you're using a bowl, wrap tightly and thoroughly in plastic wrap, making sure there's plenty of room in the bowl for the dough to rise.) Place in the refrigerator to rise for at least 8 hours or for up to 2 days.
When you're ready to bake—I've found that a 2-day rise is best, but 1 will work just fine—oil an 18 x 13-inch baking sheet. Remove the focaccia dough from the refrigerator and transfer to the prepared pan. Using your hands, spread the dough out on the prepared pan as much as possible, adding oil to the dough as needed to keep it from sticking. Place the dough in a warm place and let it rise until it about doubles in bulk The rising time will vary considerably depending on the season. (In the summer, it might take just 20 minutes; in winter, it can take an hour or more.) When the dough is ready, it should be room temperature, spread out on the sheet, and fluffy feeling.
Preheat the oven to 450°F.
Pat down the focaccia to an even thickness of about 1 inch on the baking sheet, and then make a bunch of indentations in the dough with your fingertips—like you're playing chords on a piano. Dimple the entire dough and then drizzle the whole thing again with olive oil. Sprinkle the entire surface of the focaccia evenly with sea salt.
Bake, rotating once front to back, until the top is uniformly golden brown, about 15 minutes. Transfer to a wire rack to cool, then slide out of the pan. Use the same day.