The next day, remove the cold dough from the fridge and drizzle 3tbsp olive oil into a cast iron skillet. Both 27cm and 30cm pans work well. Alternatively use a 23 x 33cm (9x13 inch) rectangular baking pan.
Rub some olive oil on your fingers and push the dough out to fill the pan. The cold dough will likely spring back at first, so press what you can and then wait 10 minutes before continuing.
Once it has filled the pan, the dough needs to rise and double until it is jiggly and puffy. This can take between 3-7 hours depending on room temperature. You can cover the dough at this point or, brush it with 1 tbsp olive oil to stop the dough drying out.
Preheat the oven to 210°C (410°F) fan-bake or 230°C (446°F) regular oven.
Once the dough has risen, use greased fingers to dimple the dough.
Press in your favourite toppings and scatter over some coarse sea salt
Bake the focaccia for 20-25 minutes until deep golden brown.
If using a cast-iron skillet, while it is hot from the oven, run a butter knife along the edge of the cast-iron skillet to loosen the edges, so that the bread can be lifted out easily.
Lift the bread from the pan and place it on a cooling rack. Serve warm.