Preheat the oven to 205C / 400F
Pour the water on top of the sugar in a large bowl, then swirl to dissolve the sugar.
Add the yeast and swirl again, then leave for 5 minutes to dissolve.
Add one cup of the flour to the sugar/water/yeast, along with the olive oil, and stir with a wooden spoon until all the flour is combined.
Add the rest of the flour and stir vigorously until a ball of dough forms.
Add a tiny bit more flour if the dough is still really sticky. Then, with floured hands, turn out onto a well-floured board or clean work surface and fold in about half of the rosemary.
Press the dough into a pan or skillet (about 10 x 7 inches or equivalent, or 8 inches in diameter), pushing it right to the edges.
Push your thumb into the dough in a few places to make indentations, then sprinkle over the rest of the rosemary and drizzle over a bit more olive oil (roughly a tablespoon).
Bake for about 20 minutes or until the bread is golden and has pulled away from the sides of the pan.
Serve warm with a dish of olive oil and balsamic vinegar (optional but highly recommended!).