Place water, 2 tablespoons olive oil, garlic, bread flour, 1 tablespoon rosemary, salt, and yeast into a bread machine in the order listed, or follow the order recommended by the manufacturer if different.
Run dough cycle. Remove dough from the machine after the cycle is done, about 90 minutes.
Lightly drizzle olive oil into a 9x13-inch baking pan.
Pat dough into prepared pan in an even layer.
Use your fingers to dimple the dough every inch or so.
Brush with remaining 2 tablespoons oil and sprinkle with remaining 1 tablespoon rosemary. Sprinkle with additional sea salt.
Cover with plastic wrap and let rest while the oven preheats, about 15 minutes.
Preheat the oven to 400 degrees F (200 degrees C).
Remove plastic wrap and bake focaccia in the preheated oven until golden brown, about 20-25 minutes. Let cool for 5 minutes before serving
Notes
Bread flour: I've also made this recipe with all-purpose flour. It works fine; it just isn't as chewy when made with all-purpose flour as it is with bread flour.
Rosemary: You can use dried rosemary if you prefer. You'll only need 1 teaspoon of dried rosemary for every tablespoon of fresh rosemary.
Salt: Use half the amount of table salt if you don't have sea salt or kosher salt.