In a large bowl, combine the softened cream cheese and sour cream.
Mix in the chopped spinach and artichoke hearts.
Add the minced garlic, salt, black pepper, and red pepper flakes.
Stir in the mozzarella and Parmesan cheeses until well combined.
Transfer the mixture into the crockpot.
Cover and cook on low for 2-3 hours, stirring occasionally.
Check for creaminess; if too thick, add a splash of milk.
Once heated through and bubbly, stir well before serving.
Serve warm with bread, crackers, or vegetables for dipping.