Prepare the Yeast Mixture: In a small bowl, dissolve sugar in warm water. Sprinkle the yeast over the water and let it sit for 5 minutes, or until foamy.
Make the Dough: In a large mixing bowl, combine flour and salt. Make a well in the center and pour in the yeast mixture and 2 tablespoons of olive oil. Mix until a sticky dough forms.
Knead the Dough: Turn dough out onto a floured surface and knead for about 10 minutes, until smooth and elastic. Add more flour if the dough is too sticky.
First Rise: Place the dough in a clean, oiled bowl and cover with a damp cloth. Let it rise in a warm place for 1 hour, or until doubled in size.
Prepare Potatoes: While the dough is rising, bring a pot of salted water to a boil. Add the potato slices and cook for 2 minutes. Drain and set aside to cool.
Shape the Focaccia: After the first rise, punch down the dough and stretch it onto an oiled baking sheet, creating a rough rectangle. Cover and let it rise for another 30 minutes.
Preheat Oven: Preheat the oven to 425°F (220°C).
Add Toppings: Gently press the potato slices, basil, and rosemary into the surface of the dough. Drizzle with olive oil and sprinkle with sea salt and black pepper.
Bake: Place the focaccia in the oven and bake for 20-25 minutes, or until golden brown.
Cool and Serve: Remove from the oven, let it cool slightly on a wire rack, then cut into squares and serve.