Preheat your smoker to 225°F using clean-burning oak or hickory wood.
In a small bowl, combine the sea salt, black pepper, garlic powder, onion powder, and smoked paprika to create a classic Texas-style dry rub.
Pat the beef brisket dry with paper towels and apply the rub generously to all sides, pressing it firmly into the meat to ensure a good crust forms.
Place the brisket on the smoker grate and cook until the internal temperature reaches approximately 165°F.
Wrap the brisket tightly in un-waxed butcher paper or aluminum foil and return it to the smoker.
Continue cooking until the internal temperature reaches 203°F and a thermometer probe slides into the meat with no resistance.
Remove the brisket from the smoker and let it rest, still wrapped, for at least 30 to 60 minutes to allow the juices to redistribute.
While the meat rests, whisk together the olive oil, apple cider vinegar, mustard, and celery seed in a medium bowl.
Toss the shredded cabbage into the dressing until thoroughly coated.
Slice the rested brisket against the grain into thin strips and serve immediately alongside the tangy slaw.