01 - In a large mixing bowl, whisk together the bread flour, kosher salt, granulated sugar, and instant dry yeast until evenly distributed.
02 - Pour in the lukewarm water and ¼ cup extra virgin olive oil. Stir vigorously with a wooden spoon or dough whisk until a sticky, shaggy dough forms and no dry flour pockets remain.
03 - Turn the dough out onto a lightly floured work surface. Knead firmly for 8 to 10 minutes, pushing with the heel of your hand and folding back, until the dough becomes smooth, elastic, and springs back when gently pressed.
04 - Lightly coat a clean large bowl with olive oil. Place the dough inside, turning once to coat all sides. Cover tightly with plastic wrap or a damp kitchen towel. Set in a warm, draft-free spot and let rise for 1 to 1 ½ hours, or until the dough has doubled in bulk.
05 - Generously drizzle olive oil across a baking sheet (approximately 12x16 inches). Gently transfer the risen dough onto the pan and stretch it out evenly using your fingertips, pressing firmly to create deep dimples across the entire surface.
06 - Drizzle 2 tablespoons of extra virgin olive oil over the dimpled dough. Scatter the fresh rosemary leaves evenly across the surface and finish with a generous sprinkle of flaky sea salt.
07 - Cover the tray loosely with plastic wrap or a towel and allow the dough to rise for an additional 30 minutes until visibly puffed. Meanwhile, preheat your oven to 425°F.
08 - Place the focaccia on the center rack of the preheated oven. Bake for 20 to 25 minutes, rotating the tray halfway through, until the top is deeply golden brown and the bottom sounds hollow when tapped.
09 - Remove from the oven and allow the focaccia to cool on the baking sheet for 5 minutes. Slide onto a cutting board, slice into squares or strips, and serve warm.