Using a serrated knife, carefully cut the sourdough loaf into a checkerboard pattern, making deep cuts about 1-inch apart.
In a mixing bowl, combine the melted butter, minced garlic, chopped parsley, basil, oregano, and red pepper flakes. Season with a pinch of sea salt and black pepper, and mix well to combine.
Gently pull apart the sections of the bread loaf and drizzle the garlic herb butter mixture generously inside the cuts.
Stuff the shredded mozzarella and cheddar cheese into the cuts of the bread for even distribution.
Sprinkle the grated Parmesan cheese evenly over the top of the loaf.
Wrap the stuffed bread loaf in aluminum foil, seal tightly, place on a baking sheet, and bake for 15 minutes.
After 15 minutes, carefully unwrap the foil and bake for an additional 10-15 minutes until the cheese is melted and the top is golden brown and crispy.
Remove from the oven, let it cool slightly, and place on a serving platter. Pull apart the sections of bread and enjoy warm.