Ingredients:
4 cups (512 g) all-purpose flour or bread flour
2 to 3 teaspoons (10 to 15 grams) kosher salt
2 teaspoons (8 g) instant yeast
2 cups (455 g) lukewarm water (1/2 cup boiling water mixed with 1 1/2 cups cold water)
Butter for greasing
4 tablespoons olive oil, divided
Flaky sea salt, such as Maldon
1 to 2 teaspoons whole rosemary leaves, optional
Instructions:
Make the Dough:
In a large bowl, whisk together the flour, salt, and instant yeast. Add the lukewarm water.
Mix with a rubber spatula until a sticky dough forms. Lightly rub dough with olive oil.
Cover the bowl with a damp tea towel or plastic wrap. Place in the refrigerator for at least 12 hours or up to three days.
Prepare Baking Pans:
Line two 8- or 9-inch pie plates or a 9×13-inch pan with parchment paper, butter, or nonstick spray.
Pour a tablespoon of oil in each pie plate (or two tablespoons if using the 9×13-inch pan).
Deflate Dough:
Use two forks to deflate the dough in the bowl by releasing edges and pulling toward the center.
Divide into two pieces (or keep whole if using the 9×13-inch pan) and place into prepared pans.
Room Temperature Rise:
Roll dough ball in oil to coat, forming a rough ball.
Let rest for 3 to 4 hours at room temperature (no need to cover).
Preheat Oven and Dimple Dough:
Preheat the oven to 425°F.
If using rosemary, sprinkle over dough. Pour more olive oil over and create deep dimples with fingers.
Sprinkle flaky sea salt over the dough.
Bake:
Bake for 25 to 30 minutes until golden and crisp.
Remove from oven, transfer focaccia to a cooling rack.
Let cool for 10 minutes before serving.
Storage:
Store cooled focaccia in an airtight container at room temperature for up to 3 days or freeze for up to 3 months. Reheat at 350ºF for 15 minutes to revive the crust.