In a large bowl or the bowl of a stand mixer, combine the warm water (350ml or 1.5 cups) and granulated sugar (1 tsp or 5g). Sprinkle the active dry yeast (7g or 2.25 tsp) over the top. Let it sit for 5-10 minutes, or until it becomes foamy and bubbly. This indicates the yeast is active and ready to use. If it doesn't foam, your yeast may be old, and you should start with fresh yeast.

Add the all-purpose flour (500g or 4 cups), fine sea salt (10g or 2 tsp), and extra virgin olive oil (60ml or 1/4 cup) to the yeast mixture. If using a stand mixer, attach the dough hook and mix on low speed until a shaggy dough forms. If mixing by hand, stir with a wooden spoon or spatula until just combined.

Increase the mixer speed to medium-low and knead for 8-10 minutes, or knead by hand on a lightly floured surface for 10-12 minutes. The dough should become smooth, elastic, and slightly sticky. It should pull away from the sides of the bowl but still be soft. Add a little more flour, a tablespoon at a time, if the dough is too sticky to handle.

Lightly grease a large bowl with extra virgin olive oil. Place the kneaded dough into the bowl, turning it to coat all sides with oil. Cover the bowl tightly with plastic wrap or a damp kitchen towel. Let the dough rise in a warm place for 1 to 1.5 hours, or until it has doubled in size.

Generously grease a 9x13 inch (23x33 cm) baking pan with extra virgin olive oil. Gently punch down the risen dough to release the air. Transfer the dough to the prepared baking pan. Gently stretch and press the dough to fill the pan. If it resists, let it rest for 5-10 minutes before continuing. You want the dough to be about 1.5-2cm (0.5-0.75 inches) thick.

Cover the pan loosely with plastic wrap or a kitchen towel and let the dough rise again in a warm place for another 30-45 minutes, or until it is puffy and has nearly doubled in thickness.

While the dough is proofing for the second time, preheat your oven to 220°C (425°F).

Once the dough has finished its second rise, uncover it. Drizzle the remaining extra virgin olive oil (about 2-3 tablespoons or 30-45ml) evenly over the surface of the dough. Using your oiled fingertips, gently dimple the dough all over, pressing down to create small indentations. Be careful not to deflate the dough completely.

Sprinkle the finely chopped fresh rosemary (2 tbsp or 10g) and flaky sea salt (1 tsp or 6g) evenly over the dimpled dough. You can also tuck a few small sprigs of rosemary into some of the dimples for visual appeal.

Bake in the preheated oven for 20-25 minutes, or until the focaccia is golden brown on top and the edges are crisp. The bottom should also be golden brown when you carefully lift an edge.

Remove the focaccia from the oven and let it cool in the pan for about 5-10 minutes. Then, carefully transfer it to a wire rack to cool slightly before slicing. For an extra glossy finish, you can brush the top with a little more olive oil while it's still warm.

Slice the focaccia into squares or rectangles, approximately 7.5cm x 10cm (3x4 inches) each, and serve warm or at room temperature.