Combine the flour and salt in a large bowl. Whisk to thoroughly combine. Dissolve the yeast in the water and add to the bowl along with 3 Tbsp olive oil. Stir together until combined then knead briefly until smooth. Cover the bowl and let rise for 40 minutes. Transfer the bowl to the refrigerator and let rest for 2 hours. This will allow the dough to fully hydrate.
Pour out the dough onto a lightly floured surface and give it a couple good kneads to smooth it out. This dough will look pretty rough when you take it out of the refrigerator, but will come back together after kneading. Using a rolling pin, roll out the dough to approximately 18" x 14". If the dough seems stiff and hard to roll, just let it rest and warm up a bit, then continue. Sprinkle 2 tsp of the rosemary and 1/3 of the olives on half of the dough closest to you running lengthwise. Fold the uncovered half of the dough over the covered half. It will now be very long and skinny (approximately 9" x 14"). Sprinkle 2 more tsp rosemary and another 1/3 of the olives on the right half of the dough, then fold the left half over the right half. Now it should be about 9" x 7".
Again using the rolling pin, roll the ingredients into the dough, making the dough around 12" x 17" or so. Pour 3 Tbsp olive oil into a baking sheet and transfer the dough to the pan. Using your fingertips, make deep depressions, or dimples, into the dough. Sprinkle a few unchopped rosemary leaves, the final 1/3 of the olives and the Parmesan cheese over the top. Cut the onion slices in half and sprinkle over top and generously drizzle more olive oil over everything. Cover well and let rest for 40 more minutes.
While the dough is resting, preheat the oven to 475 degrees. Place a pizza stone on a rack in the middle of the oven and allow to heat.
After the dough has rested, place the baking sheet directly on the pizza stone. Shut the oven door and immediately turn the oven down to 375 degrees. Bake for 15–17 minutes until the internal temperature is 200 degrees.