1. Prepare the Beef: In a small bowl, make a rub by combining the salt, pepper and cayenne. Slice the roast into 4 equal sized pieces and remove any excess fat or gristle. Rub the meat on all sides with the salt mixture then wrap each piece tightly in plastic wrap. Place the meat on a plate and allow to sit overnight in the refrigerator.
2. Place the Roast in a Slow Cooker on LOW for 6-8 hours.
3. Meanwhile, make the Blue Cheese Coleslaw: In a medium bowl, whisk together the mayonnaise, mustard, vinegar, celery salt, Kosher salt and pepper. Pour enough of the mayonnaise dressing over the shredded cabbages and grated carrots to moisten them. Add in the crumbled blue cheese and chopped parsley and toss well to combine. Cover the bowl and refrigerate for a few hours to allow the flavors to combine.
4. Make the Barbecue Sauce: Combine the onion and reserved fat in a saucepan over medium heat. Cook, stirring occasionally until the onion has softened, about 10 minutes. Add the minced garlic and chili powder and cook, stirring constantly until well combined and aromatic, about 30 seconds. Stir in remaining sauce ingredients and reserved juices and simmer until thickened, about 15-20 minutes. Allow the sauce to cool slightly before straining the sauce if you prefer a velvety texture.
5. Assemble the Sandwiches: Split and lightly toast each hamburger bun. Using 2 forks, pull the beef apart into shreds, discarding any excess fat or gristle. In a saucepan set over low heat, toss the beef with enough barbecue sauce to moisten the meat well. When heated through, place the sauced beef on top of the bottom half of each bun. Top the beef with some of the blue cheese coleslaw, add the top half of the bun and serve immediately.

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