01 - In a large mixing bowl, whisk together the flour, salt, sugar, and instant yeast until evenly distributed.
02 - Pour in the lukewarm water and olive oil. Stir with a wooden spoon or your hands until a sticky, shaggy dough comes together.
03 - Turn the dough out onto a lightly floured surface. Knead firmly for 8 to 10 minutes, until the dough becomes smooth, elastic, and springs back when pressed.
04 - Place the dough in a lightly oiled bowl, turning once to coat. Cover tightly with a damp kitchen towel or plastic wrap. Set in a warm, draft-free spot for 1 to 1½ hours, or until doubled in bulk.
05 - Generously oil a rimmed baking sheet (approximately 12x16 inches). Gently transfer the risen dough onto the pan and stretch it out to fill the edges. Press your fingertips firmly into the surface to create deep dimples across the entire dough.
06 - Drizzle the remaining olive oil evenly over the surface. Scatter the rosemary leaves and sprinkle generously with flaky sea salt.
07 - Cover the tray loosely and let the dough rest for 30 minutes until puffed and pillowy. Meanwhile, preheat the oven to 425°F.
08 - Bake on the center rack for 20 to 25 minutes, rotating halfway through, until the top is deeply golden and the bottom sounds hollow when tapped.
09 - Remove from the oven and allow to cool on the tray for 5 minutes. Slice into squares or rectangles and serve warm.