In a large mixing bowl, combine the gluten-free flour, sugar, yeast, and sea salt.

Add the warm water and 1/4 cup olive oil to the dry ingredients. Stir until just combined; the dough will be quite sticky.

Cover the bowl with a clean kitchen towel and let it rise in a warm place until doubled in size, about 1 hour.

Preheat the oven to 425°F. Grease a 9x13 inch baking pan with olive oil.

Transfer the dough to the prepared pan, spreading it out evenly with oiled hands.

Dimple the dough with your fingertips, then drizzle with additional olive oil and sprinkle with chopped rosemary and coarse sea salt.

Bake in the preheated oven for 20-25 minutes, or until golden brown and cooked through.

Remove from oven and let cool slightly before slicing and serving.