Slice the bread horizontally and vertically to create a grid, without cutting all the way through the bottom crust.
In a skillet, heat the olive oil over medium heat. Add minced garlic and cook until fragrant, about 1 minute.
Add the chopped spinach and artichokes to the skillet, cooking until the spinach wilts, around 2-3 minutes.
In a mixing bowl, combine the cream cheese, mozzarella cheese, Parmesan cheese, onion powder, red pepper flakes, salt, and pepper. Mix until thoroughly blended.
Fold in the sautéed spinach and artichoke mixture into the cheese blend until well incorporated.
Using a spoon, generously fill the crevices of the sliced bread with the spinach artichoke mixture.
Wrap the filled bread in aluminum foil and place it on a baking sheet.
Bake in the preheated oven for 15-20 minutes, or until the cheese is melted and bubbly.
Remove from the oven, unwrap the foil, and allow it to cool slightly.
Garnish with fresh chopped parsley before serving.