Combine the flour, yeast, olive oil and salt in a mixer with a dough hook.
Add the water to make a soft dough, and knead in the mixer until smooth and shiny.
Transfer to an oiled bowl, cover with a tea towel and leave in a warm place for about an hour until well risen.
Tip the mix out onto a floured surface and knead to knock out any air pockets. Roll the dough into an oval-like shape about 2cm/¾in thick. Transfer to an oiled baking tray.
Firmly press your fingers into the surface to 'pit' the surface. For the topping, drizzle with olive oil and lightly grind sea salt over the top.
Put a small sprig of rosemary into each pit.
Cover with a tea towel and set the loaf aside for another 20 minutes.
Preheat the oven to 200C/400F/Gas 6.
Transfer the loaf to the middle shelf of the oven and cook for about 15 minutes until golden brown.