In a bowl, mix the warm water, active yeast, and sugar and allow the mixture to dissolve for about 15 minutes.
Meanwhile, in a large bowl, add the flour, olive oil, salt and rosemary. Stir well with a wooden spoon to combine.
Add the water and yeast to the flour little by little, stirring every 1/2 cup or so. Dough should be shaggy when all ingredients are mixed together.
Place plastic wrap over dough and cover for about 2 hours, allowing the dough to rise in a warm space.
Once risen, knead dough for about 10 minutes into a ball. Cover the ball with plactic wrap and refrigerate for 12 to 24 hours.
After refrigerating, unwrap dough and place in a large greases bowl. Allow to rise one last time for about 2 hours.
When ready to bake, preheat oven to 400 degrees Fahrenheit. In a 13x9 sheet pan, pour in 2 tablespoons of oilvs oil. Add the dough, and gentry knead it out so it fills the sheetpan. Allow to sit for about 15 minutes. Use your fingers to poke holes in the dough, go all the way to the sheetpan. Drizzle the remaining 2 tablespoons of olive oil on top. Sprinkle top with a touch of extra salt and rosemary.
Bake focaccia for 20-25 minutes until top is golden brown. Remove from oven and allow to cool for 10 minutes before serving.