Activate the yeast: Mix warm water with sugar and yeast. Let it sit 5 minutes until foamy.
Make the dough: Add flour and salt. Stir until combined. Drizzle 1 Tbsp olive oil over the top. Mix until sticky and soft.
First rise: Cover the bowl and let the dough rise 1 hour in a warm spot until doubled.
Prepare the pan: Brush a 9×9-inch (23×23 cm) pan with olive oil. Transfer the dough, stretch it gently to fit, and let it rest 20 minutes.
Add toppings: Dimple the dough with your fingertips. Drizzle 2 Tbsp olive oil on top, then scatter garlic, rosemary, and flaky salt.
Bake: Bake in a preheated oven at 425 °F (220 °C) for 20–25 minutes, until the top is golden and crisp.
Finish and serve: Brush the warm focaccia with a bit of olive oil. Cool for 10 minutes, slice, and serve warm.