In a large mixing bowl, combine the warm water and instant yeast. Allow it to sit for about 5 minutes until it becomes frothy. This step activates the yeast, ensuring your bread rises properly.

Add the sifted flour, salt, and olive oil to the yeast mixture. Using a whisk or wooden spoon, mix until a shaggy dough forms. This helps to incorporate air into the dough, which is essential for a light texture.

Transfer the dough to a lightly floured surface and knead for about 5-7 minutes until smooth and elastic. Kneading develops the gluten, giving the bread its structure.

Place the dough in a lightly oiled bowl and cover it with plastic wrap. Let it rise in a warm place for about 30 minutes, or until it doubles in size. This is crucial for the dough to become airy and fluffy.

Preheat your oven to 425°F (220°C).

Once the dough has risen, gently punch it down to release the air. Transfer it to a greased baking sheet and stretch it out to fit the pan. Use your fingers to create dimples all over the surface of the dough; this helps to hold the olive oil and toppings.

Drizzle a bit of olive oil over the top and sprinkle with chopped rosemary and coarse sea salt. Let it rise again for 15-20 minutes while the oven heats up. This second rise enhances the texture.

Bake in the preheated oven for 20-25 minutes, or until golden brown. The baking time may vary depending on your oven, so keep an eye on it. A golden crust indicates that it’s done.

Once baked, remove from the oven and let it cool slightly on a wire rack. This prevents the bottom from becoming soggy.

Cut into squares or rectangles and serve warm. Focaccia is delicious on its own or can be used for sandwiches.