Start by ensuring your spinach is completely thawed and squeezed dry—excess moisture is the enemy of a creamy dip, so really wring it out with your hands or a clean kitchen towel. In a large mixing bowl, combine the thawed spinach, chopped artichoke hearts, cubed cream cheese, shredded mozzarella, parmesan cheese, minced garlic, milk, sour cream, red pepper flakes, salt, and black pepper. Stir everything together until the cream cheese begins to soften and the ingredients are evenly distributed throughout the mixture.

Transfer the combined ingredient mixture from Step 1 into your crockpot. Cook on high heat for about 2 hours, stirring frequently—I recommend stirring every 15-20 minutes to ensure even melting and prevent the edges from sticking. The dip is ready when the cream cheese is completely melted, all cheeses are integrated, and the mixture is hot, creamy, and uniform in texture. The dip should be warm and easily scoopable by the end of cooking.