Combine salt, pepper, and allulose, and spread liberally all over the brisket.
Smoke in a smoker for 4 hours at 200F. After 3.75 hours, preheat oven to 250 F.
Transfer brisket to oven bag. Tie tightly, and place on a baking tray in oven. Cook for 4 hours.
Remove from oven. Allow to rest in the bag for 5 to 10 minutes. Transfer to cutting board. Pour drippings into a saucepan and bring to a boil with glucomannan powder for one minute. If sauce is too salty, cut with heavy cream.
Slice brisket against the grain and serve with sauce. Enjoy!