Trim the beef brisket of excess fat, leaving a thin quarter-inch layer to keep the meat moist during the long cook.
Whisk together the sea salt, black pepper, and garlic powder in a small bowl to create a classic Texas-style dry rub.
Apply the dry rub generously to all sides of the brisket, pressing it firmly into the meat to ensure a good crust forms.
Preheat your smoker to 225°F using oak or hickory wood for a clean, authentic smoke flavor.
Place the brisket on the smoker and cook until the internal temperature reaches 165°F, typically taking several hours.
Remove the brisket and wrap it tightly in peach butcher paper, then return it to the smoker to finish cooking.
Continue smoking until the internal temperature reaches 203°F and the meat feels tender when probed.
Allow the brisket to rest in a room-temperature cooler for at least one hour to let the juices redistribute.
While the meat rests, whisk the apple cider vinegar, olive oil, and celery seed together and toss with the shredded cabbage.
Slice the rested brisket against the grain into thin strips and serve immediately alongside the fresh slaw.