In a large bowl, combine the gluten-free flour blend, tapioca starch, yeast, sugar, and salt. Mix well.
Add the warm water and olive oil to the dry ingredients and mix until a dough forms.
Knead the dough on a floured surface for 2-3 minutes until it becomes smooth and elastic.
Place the dough in a greased bowl, cover with a damp towel, and let it rise in a warm place for about 30 minutes.
Preheat your oven to 400°F (200°C).
Grease a 9-inch (23cm) baking dish with olive oil.
Once the dough has risen, transfer it to the greased baking dish and press it down evenly.
Drizzle olive oil on top of the dough and use your fingers to create dimples in the dough.
Sprinkle coarse sea salt, Italian seasoning, garlic powder, and onion powder over the top of the dough.
If desired, add some fresh rosemary to the top of the dough.
Bake for 20-25 minutes, or until the focaccia is golden brown and sounds hollow when tapped.
Remove from the oven and let it cool for a few minutes before slicing and serving.