In a large mixing bowl, combine the all-purpose flour, salt, and instant yeast.
Add the warm water to the dry ingredients and stir with a wooden spoon or spatula until a shaggy dough forms.
Add the shredded sharp cheddar cheese and shredded mozzarella cheese to the dough and gently fold them in until evenly distributed.
Cover the bowl tightly with plastic wrap or a clean kitchen towel and let the dough rise at room temperature for 12 to 14 hours, or until the surface is bubbly and doubled in size.
After the dough has risen, preheat your oven to 450°F (230°C). Place a Dutch oven or heavy oven-safe pot with a lid inside the oven to heat up for 30 minutes.
While the oven and pot are heating, sprinkle garlic powder over the olive oil and brush the inside of the Dutch oven or pot to prevent sticking and add flavor.
Turn the dough out onto a well-floured surface and shape it gently into a round loaf without kneading.
Carefully remove the hot Dutch oven from the oven and place the dough inside. Cover with the lid and bake for 30 minutes.
After 30 minutes, remove the lid and bake for an additional 15 minutes, or until the bread is golden brown and crusty.
Remove the bread from the oven and transfer it to a wire rack to cool completely before slicing.