Start by placing the flour into a large mixing bowl. Then, sprinkle the yeast on one side and the measured sea salt on the opposite side; it’s crucial they don't touch at this stage. This way, you ensure the yeast remains active for rising.
Create a small well in the center of the flour blend. Pour in the lukewarm water and add the olive oil. Using a table knife, mix everything together gently until a shaggy dough forms.
Transfer the dough onto a clean surface. Knead it for about 4 to 6 minutes until it becomes smooth and elastic. It's a great workout! Dust the surface with a little more flour if it starts to stick.
Once kneaded, brush the surface of the dough with a bit of olive oil and place it in a clean, oiled bowl. Cover it with plastic wrap and let it rise in a warm spot until it doubles in size, which will take about 1 hour.
Preheat your oven to 400°F (200°C). Meanwhile, grease a large baking tray.
Gently scoop the risen dough from the bowl and place it onto the prepared baking tray. Flatten it gently into a rectangle, being careful not to deflate it too much. Brush the top lightly with more olive oil.
Cover the dough again with plastic wrap and let it rest in a warm spot for another 30 minutes or until it has doubled in size.
After the second rise, use your fingers to slightly press down on the surface of the dough, creating small pockets. This is what gives focaccia its character! Sprinkle generously with fresh rosemary and sea salt flakes, then drizzle more olive oil over the top.
Bake in the preheated oven for 25 to 30 minutes or until the focaccia is golden brown and cooked through. Your kitchen will smell divine!
Once baked, transfer the focaccia to a wire rack to cool slightly. Slice it warm and serve it up with your favorite accompaniments.