Grease & line a 9”x13” baking tin then pour in 2 tbsp of the rosemary oil.
Tip the dough into the tin & gently spread it out with your hands. Don't worry if it doesn't completely fill the tin at this point.
Cover the dough loosely with clingfilm (or an upside down tin) & leave at room temperature for 1½ - 2 hours, until the dough has risen slightly & is very bubbly.
Whilst your dough is proving, preheat an oven to 220°c/200°c fan (430°f/390°f).
Once the dough has risen, spoon 2-3 tablespoons of rosemary oil over the focaccia & use your fingers to dimple the dough all over, making sure that the dough reaches all corners of the tin.
Sprinkle the focaccia with a generous amount of Maldon salt then bake until a deep golden brown, 25-30 minutes.
Once baked, brush the focaccia with 1 tbsp of rosemary oil, leave to cool in the tin for 30 minutes then transfer to a cooling rack to cool completely before serving.