In a mixing bowl, combine the warm water and sugar. Sprinkle the instant yeast over the top and let it sit for about 5 to 10 minutes, or until it becomes frothy.
In a separate bowl, whisk together the gluten-free all-purpose flour blend, baking powder, and 1/2 teaspoon of salt.
Once the yeast is frothy, add the flour mixture to the yeast mixture along with 2 tablespoons of olive oil, chopped rosemary, and minced garlic (if using). Stir until a thick, sticky dough forms.
Grease a baking sheet with the remaining 1 tablespoon of olive oil. Transfer the dough to the baking sheet and spread it out to fill the pan, creating dimples all over the surface.
Cover the dough with a clean kitchen towel and let it rise in a warm place for about 30 to 45 minutes, or until it has puffed up slightly.
Preheat your oven to 425°F (220°C).
Once the dough has risen, sprinkle the remaining 1/2 teaspoon of salt over the top, drizzle with more olive oil, and bake for 20-25 minutes until golden brown.
Remove from the oven and allow to cool for a few minutes before slicing. Serve warm or at room temperature.