Rub the inside of a slow cooker with about 1 tablespoon oil and turn on Low heat. Mix salt, black pepper, garlic powder, paprika, 1 teaspoon cumin, onion powder, chili powder, and cayenne pepper together in a bowl. Rub spice mixture all over pork. Top pork with cornstarch and pat in to coat completely. Heat remaining oil in a heavy skillet over medium-high heat. Sear pork in the hot oil on all sides until almost black, about 5 minutes. Transfer seared pork to the slow cooker. Reduce heat to medium and pour beef stock into the skillet. Whisk until boiling, scraping up browned bits, about 5 minutes. Boil gently for 3 to 4 minutes more. Strain stock into the slow cooker. Add salsa, Hatch chiles, diced tomatoes, and potatoes. Combine tomatillos, 1/2 the cilantro, jalapeno pepper, Anaheim pepper, serrano pepper, remaining cumin, and liquid smoke in a blender. Blend on high power and add to slow cooker. Cover and cook on Low for 8 hours. Remove pork from slow cooker and shred using 2 forks. Return meat to slow cooker. Season with additional salt and pepper. Serve chili in bowls with Mexican cheese, sour cream, and remaining cilantro.