01 - Combine bread flour, instant dry yeast, and fine sea salt in a large bowl; mix thoroughly.
02 - Add warm water and olive oil to the dry ingredients and stir until a sticky dough forms.
03 - Knead on a lightly floured surface for 8 to 10 minutes until smooth and elastic, or use a stand mixer with dough hook for 6 to 8 minutes.
04 - Place dough into a clean, oiled bowl; cover with plastic wrap or damp towel and let rise in a warm place until doubled in size, approximately 1 hour.
05 - Lightly oil a 9x13-inch baking pan, transfer the risen dough, and gently stretch to fill the pan.
06 - Cover dough and let it rise again for 30 to 40 minutes until puffed.
07 - Preheat the oven to 425°F.
08 - Mix olive oil, minced garlic, and chopped rosemary in a small bowl.
09 - Dimple the dough surface using fingers, drizzle the garlic-herb oil evenly, ensuring it fills indentations, then sprinkle flaky sea salt.
10 - Bake for 22 to 25 minutes or until golden brown and crisp on top.
11 - Allow focaccia to cool slightly before slicing and serving.