In a small saucepan, combine the honey, bourbon, ketchup, brown sugar, soy sauce, cider vinegar, Worcestershire, garlic, smoked paprika, black pepper and red pepper flakes. Bring to a gentle simmer over medium heat and cook for 3 to 4 minutes, stirring, until the sugar dissolves and the sharp alcohol smell softens.
Lightly grease a 6-quart slow cooker. Add the frozen meatballs in an even layer, pour the warm sauce over them and stir until every meatball is coated.
Cover and cook on LOW for 3 to 4 hours or on HIGH for 2 to 2 1/2 hours, stirring once about halfway through, until the meatballs are hot all the way through and read 165°F (74°C) in the center.
Whisk the cornstarch with the cold water until smooth. Stir the slurry into the crockpot, cover, and cook on HIGH for 15 to 20 minutes, until the sauce turns glossy and coats the back of a spoon.
Switch the slow cooker to WARM. Scatter the green onions and sesame seeds over the top and serve with toothpicks, or spoon the meatballs over rice for a main dish.