In a mixing bowl, combine the warm water and sugar. Sprinkle the active dry yeast over the top and let it sit for about 5-10 minutes until it becomes frothy.
Once the yeast is activated, add the flour and sea salt to the bowl. Pour in 4 tablespoons of olive oil. Mix with a wooden spoon or your hands until a shaggy dough forms.
Transfer the dough to a lightly floured surface and knead for about 5-7 minutes until it becomes smooth and elastic. If the dough is too sticky, add a bit more flour as needed.
Place the dough in a lightly greased bowl, cover it with plastic wrap or a damp towel, and let it rise in a warm place for about 1-2 hours or until it doubles in size.
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 sheet.
Cover the dough again and let it rise for another 30-45 minutes until it puffs up.
While the dough is rising, preheat your oven to 425°F (220°C).
Drizzle the remaining 2 tablespoons of olive oil over the surface of the dough. Use your fingers to create dimples all over the dough, then sprinkle with flaky sea salt and chopped fresh rosemary, or any other toppings you desire.
Bake the focaccia in the preheated oven for about 20-25 minutes, or until golden brown.
Remove the focaccia from the oven and let it cool for a few minutes before slicing.
