BOIL WATER in a large pot over high heat. Adding the macaroni pasta and cook until they are soft but not mushy. We even like them slightly al dente for more chewability, but it's a fine line to perfection. So you can also go with your favorite approach or the manufacturer's instructions).
DRAIN NOODLES and put them into an oiled casserole dish.
LAYER CHEESES on top of the noodles in casserole dish starting with the Velveeta, then the mozzarella, and last the cheddar. If using a crockpot, you'll need to do 2 layers, since it is a more vertical container.
ADD MILK, (it should be up to approximately 1/3 of the container).
COVER with aluminum foil and BAKE at 350°F for about 20 minutes.
STIR - Remove the macaroni from the oven, uncover it, and stir all the cheese milk and noodles together gently, starting in one corner and slowly working your way through the dish until there is a creamy consistency throughout. If it seems too thin, that will go away after a little longer in the oven.
COOK uncovered for another 15 minutes or so. We like to cook it until it's tinged with golden brown here and there for some crispier sections amongst the creamy bites.
SERVE hot and enjoy!