Prepare the Slow Cooker: Lightly coat the inside of a 4- to 5-quart slow cooker with nonstick cooking spray if desired for easier cleanup.

Drain the Rotel: Pour the Rotel tomatoes into a fine-mesh strainer and let them drain thoroughly. Press lightly with the back of a spoon to remove excess liquid without crushing the tomatoes.

Add the Chicken: Spread the 4 cups (560 g) shredded cooked chicken evenly over the bottom of the slow cooker. This ensures that the chicken absorbs the flavors from the other ingredients as they cook.

Add the Creamy Ingredients: Scatter the cubed cream cheese over the chicken. Add the sour cream, Buffalo sauce, drained Rotel, ranch seasoning, and garlic powder. This combination will create a rich and flavorful base for the dip.

Begin Slow Cooking: Cover and cook on LOW for 1 hour 30 minutes. The cream cheese should be very soft around the edges and beginning to melt, which will help in blending the ingredients smoothly.

Stir Until Creamy: Remove the lid and stir thoroughly, breaking up any remaining cream cheese pieces. The mixture should become thick, creamy, and evenly orange-red, indicating that the ingredients are well combined.

Continue Cooking: Cover and cook on LOW for another 30 minutes, until the mixture is hot throughout. This step ensures that all flavors meld together and the dip is heated evenly.

Add the Shredded Cheese: Stir in the cheddar and Monterey Jack until evenly distributed. This will enhance the creaminess and flavor of the dip.

Melt the Cheese: Cover and cook on LOW for another 20 to 30 minutes, stirring once halfway through, until the cheese is fully melted and the dip is smooth. This step is crucial for achieving the desired texture.

Check the Temperature: Stir well and check the center with an instant-read thermometer. Since the dip contains previously cooked chicken, it should reach at least 165°F (74°C) before serving to ensure food safety.

Adjust the Consistency: If the dip seems too thick, stir in 1 to 2 tablespoons (15 to 30 ml) of milk at a time until it reaches a creamy, scoopable consistency. If it seems thin, leave the lid slightly ajar and cook for another 10 minutes to allow excess moisture to evaporate.

Rest Briefly: Switch off the slow cooker and let the dip stand for 10 minutes. It will thicken slightly as it settles, making it easier to scoop.

Garnish and Serve: Top with green onions, crumbled blue cheese, or an extra drizzle of Buffalo sauce if desired. This adds a fresh touch and enhances the presentation.

Keep Warm for Serving: Use the WARM setting for serving, stirring occasionally. Do not leave the dip at room temperature for more than 2 hours to ensure food safety.