Spray an approx. 10x15 inch cake pan with a non-stick cooking spray.
In a large mixing bowl, mix the yeast, sugar and water. Let sit until foamy (about 5 min)
Stir in 3 tbsp. olive oil.
Add the 2 tsp. salt and ½ of the flour and stir until mixed. Continue stirring and add in enough of the remaining flour to form a soft but not sticky dough.
Turn dough out onto a floured surface and knead until smooth and satiny (about 10 minutes.)
Oil a large bowl and place dough into it, turning once to coat top with oil. Cover and let rise in a warm area until double (about 1½ hours.)
When doubled, roll dough into a rectangle to fit the size of your prepared pan. Place dough in pan and push it into the corners with your fingertips.
Cover pan with a damp towel and let rise for about 45 minutes until not quite doubled.
After risen, use your fingertips to push dimples into dough, across the entire surface. Push fingers deep into the dough, almost to the pan.
Cover with the damp towel and let rise for another 45 minutes.
Preheat oven to 425 degrees.
After rising, place sprigs of the Rosemary into each dimple. Sprinkle 4 tbsp. olive oil across the top, allowing the oil to run into the dimples. Sprinkle with the sea salt if desired.
Place pan into oven. Spray sides and bottom of the oven with water (the steam helps develop the crust of the bread).
After 5 min. of baking, spray oven again and continue to bake for about 20 minutes until golden brown. Remove to wire rack to cool.