01 - Preheat your oven to 300°F and position the rack in the center position.
02 - In a small bowl, combine the kosher salt, black pepper, smoked paprika, garlic powder, onion powder, and ground cumin. Mix thoroughly to distribute spices evenly.
03 - Pat the beef brisket dry with paper towels, then rub the spice mixture generously over all surfaces of the meat, pressing gently to adhere.
04 - Heat olive oil in a large Dutch oven over medium-high heat until shimmering. Sear the brisket on all sides until deeply browned, approximately 2 to 3 minutes per side.
05 - Remove the brisket and set aside briefly. Add the sliced onion and smashed garlic to the pot, sautéing for about 2 minutes until fragrant and slightly softened.
06 - Return the seared brisket to the pot. Pour in the beef broth. Cover tightly with a heavy lid and transfer to the preheated oven.
07 - Braise for 4 hours, turning the meat halfway through cooking. The brisket is done when a fork slides easily into the thickest part.
08 - While the brisket cooks, combine ketchup, apple cider vinegar, brown sugar, Worcestershire sauce, Dijon mustard, smoked paprika, garlic powder, onion powder, and cayenne in a saucepan. Simmer over low heat for 15 minutes, stirring occasionally, until thickened and coating the back of a spoon. Season with salt and pepper.
09 - Remove the brisket from the oven and let rest for 15 minutes. Using two forks, shred the meat, discarding any large pieces of excess fat. Toss the shredded brisket with half of the prepared BBQ sauce.
10 - Brush the cut sides of the slider buns with melted butter. Place on a baking sheet and toast in the oven for 3 to 5 minutes until golden brown.
11 - Place a generous portion of BBQ brisket on the bottom half of each bun. Top with a halved slice of cheddar cheese and a spoonful of coleslaw. Drizzle with additional BBQ sauce if desired and crown with the bun tops.
12 - Arrange the sliders on a platter and serve immediately while the cheese is melty and the buns are warm.