In a large bowl, combine the bread flour, yeast, salt, and sugar. Stir the dry ingredients together and make a well in the centre. Add in the warm water as well as 3 tablespoons of olive oil, and, using a wooden spoon, stir for 1 to 2 minutes until a stretchy, wet dough forms.
Grease a large clean bowl with 1 tablespoon of olive oil and transfer in the dough. Cover with a piece of plastic wrap or a dinner plate and set aside in a warm spot for 15 minutes.
After 15 minutes, dampen your hands and lift and stretch the dough onto itself, bringing the edges into the centre to form a tight skinned ball. Flip the dough over so that it is seam side down, recover the bowl, and set aside in the warm spot for 30 minutes. Repeat the folding one more time and cover and set aside for 1 hour or until doubled.
Add 1 tablespoon of oil into a 9-inch square baking pan and transfer the dough into the pan. Drizzle the remaining tablespoon of oil over the dough and lightly stretch into the corners of the pan, being careful not to punch all the air out. Lightly cover the pan with a clean dish towel and set aside in a warm spot for 1 to 1 ½ hours until puffy.
Heat your oven to 475ºF. Dampen your fingers with water or a little oil and press into the dough to dimple the surface. Bake for 16 to 18 minutes or until golden and springy. Remove the focaccia from the pan to cool on a wire rack.
