Proof the yeast: Whisk the yeast and sugar into the lukewarm water and set aside to proof for 10-15 minutes.
Mix dry ingredients: Add the flour, 1 ½ tsp or the rosemary, 1 tsp of the garlic powder, and 1 tsp of the salt to the bowl of your mixer equipped with the dough hook. Mix on low speed for 1 minute.
Add in wet ingredients: Add the yeast mixture and ½ cup of the olive oil to the bowl of your mixer. Start on low speed, and move up to medium speed to mix the dough. Mix for 5-6 minutes until the dough is smooth, soft, and slightly sticky. If needed, you can add more flour, 1 tbsp at a time, while the dough is mixing.
First rise: Oil a large mixing bowl and place the dough in it. Cover with plastic wrap or a clean kitchen towel and allow the dough to raise in a warm, draft-free environment for at least 1 hour or until doubled in size.
Prep a pan: Generously oil a 15"x10" jelly roll pan, making sure to coat the sides as well.
Place the dough in the pan: Turn the dough out of the mixing bowl into the jelly roll pan. Use your hands to stretch the dough across the pan, reaching all the edges. Use your fingers and a firm touch to create deep finger holes all over the dough.
Second rise: Let the dough rise in the pan for another hour or until doubled in size. Meanwhile, preheat the oven to 425F°.
Make the oil topping: Whisk the remaining oil with the remaining rosemary, garlic powder, and salt. Drizzle the mixture over the dough, and use a brush to gently even out the oil over the surface to the dough.
Bake: Bake for 20-25 minutes, or until the top turns golden brown. Let the focaccia cool in the pan for 10 minutes, then carefully loosen it with a thin spatula and let it finish cooling on a wire rack.