01 - Heat the oven to 375°F.
02 - In a large mixing bowl, blend cream cheese, sour cream, and mayonnaise until smooth.
03 - Mix in mozzarella, Parmesan, garlic, salt, black pepper, and red pepper flakes if using.
04 - Fold chopped spinach and artichoke hearts into the cheese mixture evenly.
05 - Transfer the dip into a medium oven-safe baking dish and spread evenly.
06 - Bake for 20 to 25 minutes until bubbling and golden on top.
07 - Place baguette slices on a baking sheet and brush both sides lightly with olive oil.
08 - Toast in the oven for 7 to 10 minutes, turning once, until golden and crisp.
09 - Serve the hot dip immediately alongside toasted baguette slices.