In a large bowl, stir together the flour, sugar and yeast.
Make a well in the centre, pour in the warm water and stir till the flour is fully incorporated.
Stir in the salt until combined.
With a wooden spoon or silicone dough scraper, work in as much olive oil as you can. It's ok if a little remains pooled around the dough.
Cover the bowl with cling wrap or a dish towel and let it rest for 30 minutes.
Remove the cling wrap and, with greased hands, gently lift the dough's edge with one hand and stretch and lift it over itself. Repeat on the other sides.
Cover the dough with cling wrap and let it rise until doubled in size. Approximately 1½ to 2 hours.
Once the dough has doubled, divide it in half.
Preheat the oven to 375 F.
Grease a rimmed baking sheet with olive oil. (I used a 12x17½ baking sheet)
Place half the dough onto the greased baking sheet and stretch it out to the edges. (It's OK if your dough doesn't reach the edge completely.)
Scatter half the grapes over the dough and press down firmly.
Sprinkle with 1 tbsp of sugar and 1 tsp of chopped rosemary.
Drizzle over 1 tbsp of olive oil.
Stretch out the remaining dough on a work surface and top over the first grape-layered dough.
Repeat with a sprinkle of the remaining sugar, pressing down firmly, the rosemary and olive oil.
Bake in a preheated oven at 350F for about 35 minutes or until the dough is golden brown and the bottom is crispy.