Combine cream cheese, sour cream, Parmesan, garlic powder, salt, and pepper in a bowl until smooth.

Fold in drained spinach and chopped artichokes, then stir in half the mozzarella.

Transfer mixture to the crock pot and top with remaining mozzarella.

Cook on low for 1.5–2 hours, stirring once; cook longer on low if using a larger slow cooker.

Sprinkle red pepper flakes if desired and serve warm with chips or bread.