In a large bowl, whisk together flour and salt and form a well in the middle. Add cold water and 3 tablespoons of olive oil. Start mixing the dough with a fork, incorporating the flour little by little.
Once the dough has come together, start kneading it with your hands. Knead the dough for 8 to 10 minutes, until smooth. When the dough is ready, wrap it well with plastic wrap, being sure to expel all the air so your dough doesn’t dry out, and let it rest for an hour at room temperature.
Preheat oven to 480°F/250°C.
Divide the dough into two equal parts and roll each piece out on a floured surface with a floured rolling pin, trying to keep them as round and as thin as possible. I rolled these ones a little thick, because we find it easier to handle when it’s more sturdy, but traditionally it should be almost transparent.
Grease a round pizza tray (not the type with holes in it, or you will have a very messy oven) or baking dish with olive oil. Place one layer of dough on the bottom of the dish. Add the cheese in pieces using your hands.
Cover the cheese with the second sheet of dough. Use a knife or a pair of kitchen shears to remove any excess dough from around the edges of the pan.
Seal the edges by pinching them together. Snip small holes into the top layer of dough so that the steam can escape during baking. Brush with extra virgin olive oil and sprinkle with salt.
Bake in centre of oven for 6 – 8 minutes, until golden. When the focaccia is done, remove it from the oven and let cool enough to be handled.