01 - Preheat oven to 375°F. Lightly grease a medium baking dish measuring 1.5 to 2 quarts.
02 - In a large mixing bowl, combine cream cheese, sour cream, and mayonnaise. Mix until smooth and fully incorporated.
03 - Fold in spinach, artichoke hearts, garlic, Parmesan cheese, and half of the mozzarella. Season with salt, black pepper, and red pepper flakes to taste.
04 - Spread the mixture evenly into the prepared baking dish. Top with remaining mozzarella cheese.
05 - Bake for 20 to 25 minutes until the dip is bubbly and the top is lightly golden brown.
06 - While the dip bakes, slice the baguette. Toast the slices lightly if desired.
07 - Transfer the warm dip to a serving dish and serve immediately with toasted baguette slices.