In a large mixing bowl, combine the bread flour, instant yeast, and salt.
Add the warm water and olive oil, then mix until a sticky dough forms.
Knead the dough by hand for 8–10 minutes or with a stand mixer for 6–8 minutes until smooth and elastic.
Transfer the dough to a lightly oiled bowl, cover, and let it rise for 2 hours, or until doubled in size.
Generously oil a 9×13-inch baking pan and transfer the dough into the pan.
Gently stretch the dough to fill the pan. Cover and let it rest for 30 minutes.
Preheat the oven to 425°F (220°C).
Drizzle the dough with the remaining olive oil and use your fingertips to press deep dimples across the surface.
Sprinkle with chopped rosemary, flaky sea salt, and black pepper.
Bake for 22–25 minutes, or until the top is golden brown and the edges are crisp.
Remove the focaccia from the pan and cool on a wire rack for 10 minutes before slicing.