Lightly grease your crockpot, then place 2 chicken breasts in the bottom.
Sprinkle with garlic powder, then add Rotel (or diced tomatoes) and 1 cup barbecue sauce over the top.
Cover and cook on Low for 4 hours, or until the chicken is fully cooked and tender.
Remove the chicken, shred it with a hand mixer, stand mixer, or two forks, and return it to the crockpot. Stir everything together.
Add cubed Velveeta cheese, stir gently, and cover again. Continue cooking on Low for about 15–20 minutes, or until the cheese is fully melted and the mixture is creamy.
While the cheese melts, bake tater tots according to package instructions until crispy and golden.
To serve, place a layer of tater tots in a baking dish, then spoon the cheesy BBQ chicken mixture on top.
Optional: Garnish with green onions.