In a small bowl, combine warm water with yeast and sugar. Stir to combine. Set aside.
In a large mixing bowl stir together flour and salt.
Once the yeast mixture starts to bubble up, about 5 minutes, add it to the flour.
Stir together until you have a sticky dough.
Top dough with a couple tablespoons of olive oil. Cover bowl with plastic wrap and refrigerate overnight, about 10-12 hours.
Pour 2-3 tablespoons of olive oil in a 13x9 inch oven safe casserole dish.
Make sure both the bottom and the sides of the dish are also well oiled.
Uncover dough and place in prepared casserole dish.
Gently push dough out to flatten just slightly. Be careful not to press out all the bubbles in the dough.
Cover dish with plastic wrap and allow the dough to rest for 2-4 hours. Dough will spread out to the corners, form more bubbles, and increase in size.
Preheat oven to 425°F.
Remove plastic wrap from casserole dish. Oil fingertips and press them all over the top of the dough to form dimples all over the surface.
Drizzle the dimpled dough with 1-2 more tablespoons olive oil, and sprinkle with Rosemary and salt.
Bake for 30-40 minutes until a rich golden brown.
Remove from oven and remove Focaccia bread from the baking dish right away.
Cool on a wire rack for 10-15 minutes before slicing.