In a large bowl, add the flour and icing sugar. Place the yeast on one side of the bowl and the salt on the opposite side before mixing, this helps prevent the salt from damaging the yeast.
Make a well in the centre and add the wet ingredients. Mix with a spatula until you have a wet, sticky dough.
Drizzle the dough with olive oil, cover, and leave in a warm place for 15 minutes. Perform the first set of stretch and folds: turn the bowl 90°, lift and fold the dough over itself, and repeat four times. Wet your hands to prevent sticking. Repeat this process three times in total, resting the dough for 30 minutes between each set. The dough will become bubbly and airy.
After the final fold, leave the dough to prove for 1 hour until risen and puffy.
Lightly oil a shallow rectangular tin (25cm by 35cm) and gently tip the dough in, stretching it into the corners. Cover with a tea towel and leave to prove at room temperature for another hour.
Preheat the oven to 220°C (Gas Mark 7). Press your fingers firmly into the dough to create deep focaccia dimples, this helps trap olive oil and creates the classic focaccia texture. Drizzle generously with olive oil, sprinkle with sea salt, and bake for 18–22 minutes, or until golden and crisp.
