First mix in a bowl the flour and dried yeast.
Note: if you are using fresh yeast, mix it with sugar until fluid, then stir into the wet ingredients, then add flour (see the video).
In a separate bowl, larger, pour 250 ml warm water (not hot), 3 tablespoons olive oil, 1 teaspoon sugar and 1 teaspoon salt.
Pour the flour, gradually, stirring with a wooden spoon. When the dough becomes too thick to stir, start kneading. Knead until the whole flour is incorporated.
Put the dough in a lightly oiled bowl, cover with plastic wrap and leave to rise in a warm place for 45 minutes – 1 hour (or until doubled in size)
Put the risen dough in an oiled baking sheet (25/35cm / 9.84/13.7 inches). Press and stretch the dough with your palms all over the baking sheet. Let the dough rest for 10 minutes.
Poke the dough with your fingers to make little holes.
Drizzle the dough with a mixture of 2 tablespoons olive oil and 1 tablespoon water. Sprinkle oregano (and sea salt, if you wish) and let the dough rest for another 15 minutes.
Place focaccia in the preheated oven (on 200ºC/ 392ºF) for 30 minutes or until golden and cooked through.