Lay the burger slices on the grates of the pre-heated smoker (at 225 F). Smoke them until their internal temperature reaches 15 F.
Increase the temperature of the smoker to 435 F after removing the hamburgers. Season ground beef by apply mustard oil, salt, garlic powder, and onion powder on it. Make sure you spread the seasoning all over the beef before cutting it into small patties.
Place ground beef patties on the smoker and smoke for 30 minutes until the internal temperature of the patties is 165 F. Now, assemble the buns and patties with toppings of your choice.