Trim the brisket. Remove any silver skin or excess fat from the flat muscle, and square the edges and ends of the flat. Flip the brisket and trim the fat cap to no more than ¼ inch thickness.
Return the brisket to the smoker and close the lid and continue cooking at 225°F until the internal temperature of the brisket reaches 203°F in the thickest part of the meat (another 6-8 hours of cooking).