Begin by sifting the flour into a spacious mixing bowl. On one side of the bowl, incorporate the yeast, and on the opposite side, add the fine salt. This method ensures the yeast remains active by avoiding direct contact with the salt initially. Blend all ingredients thoroughly.

Create a well in the center of your flour mixture and pour in 2 tablespoons of olive oil along with 350-400ml of lukewarm water, adding the water gradually until a slightly sticky dough forms. It's possible you won't need all the water. Dust your work surface with flour and transfer the dough onto it, ensuring to scrape the sides of the bowl clean. Knead the dough for 5-10 minutes until it becomes soft and less sticky. Place the dough in a clean bowl, cover it with a tea towel, and let it rise for 1 hour or until it has doubled in size.

Lightly oil a shallow rectangular tin measuring approximately 25 x 35cm. Transfer the dough back onto the work surface, then stretch and shape it to fit the tin. Cover with a tea towel and allow it to rise again for another 35-45 minutes.

Preheat your oven to 220C/200C fan/gas 7. Using your fingers, press dimples into the dough. Combine 1½ tablespoons of olive oil with 1 tablespoon of water and the flaky sea salt, then drizzle this mixture over the dough. Insert the rosemary sprigs into the dimples you created.

Bake the focaccia in the oven for 20 minutes or until it turns golden brown. While the bread is still hot, drizzle an additional 1-2 tablespoons of olive oil over it. Once baked, cut the focaccia into squares and serve either warm or cold, accompanied by extra olive oil if desired.