• In the morning or the evening before**, feed your sourdough starter. Let it rise until doubled in size. 
• In a large bowl, add water, sourdough starter, flour and salt. Use a rubber spatula or wooden spoon to combine it all together into a wet and shaggy dough.
• Over a period of 2 hours, perform 4 sets of stretch and folds, one every 30 minutes.
• A stretch and fold method is when one side of the dough is stretched up and pulled over itself. The bowl is then turned and this move is repeated on the following side. Continue stretching and folding and turning the bowl until all sides have been folded. That is one set of stretch and folds. The first set of stretch and folds will be very shaggy and the dough will rip easily. As the folds are carried out over the next while, the gluten structure is created and the dough gains strength.
• Each time the dough sits, cover the bowl with a damp kitchen towel to stop the top of the dough from drying out.

Bulk fermenting

• After the final stretch and fold the dough rise at room temperature around for 2-4 hours. There should be signs of bulk fermentation happening in the dough with many bubbles appearing.
• This depends on the temperature of your kitchen. A cooler kitchen will the dough to sit a bit longer, or you can create a warm spot by placing a mug of boiled water in a turned-off oven.
• Transfer the dough to an airtight container or cover the bowl with plastic wrap.
• Place it in the fridge overnight, or for up to 36 hours for an extra-long ferment.

Shaping

• Drizzle the bottom of the baking tray with a generous amount of olive oil. You can line the pan with parchment paper as well if you think your pan might stick.
• Transfer the cold dough to the oiled pan.
• Leave it to sit and rest for 10 minutes, then oil your fingers and press your fingertips into the dough to spread the dough out into the pan. If the dough resists stretching out, give it a rest and try again in a few minutes.
• Let the focaccia dough rise in a warm place until it is jiggly and puffy. This can take anywhere between 3-5 hours depending on the room temperature.
• Cover the dough at this point or, brush it with extra virgin olive oil to stop the top of the dough from drying out.
  

Dimpling and topping

• Preheat the oven to 450°F/230°C.
• Drizzle a little olive oil over the surface of the dough, then use oiled fingers to create deep dimples on the top of the focaccia dough, pushing all the way down. Do this all over the entire surface.
• Press sliced olives deep into the dough. Press the rosemary leaves. Sprinkle the dough with flaky salt.
• Bake the focaccia for around 25-30 minutes until puffed and deep golden brown and the bread pulls away from the edges of the baking dish. If the top start browning too much, loosely cover the bread with aluminum foil.
• Remove it from the oven and let it sit for 3-4 minutes. Carefully remove it from the pan then let it cool further on a wire cooling rack before serving.