01 - In a small bowl, mix salt, pepper, paprika, garlic powder, onion powder, thyme, and brown sugar. Rub the seasoning mixture all over the brisket, ensuring even coverage on all sides.
02 - Place the seasoned brisket in the slow cooker. In a separate bowl, whisk together beef broth, Worcestershire sauce, apple cider vinegar, and Dijon mustard. Pour this liquid mixture evenly over the brisket.
03 - Cover the slow cooker with its lid. Cook on low heat setting for 8 hours, or until the brisket is fork-tender and shreds easily with minimal resistance.
04 - Transfer the cooked brisket to a cutting board. Using two forks, pull the meat apart into shreds, discarding any large pieces of excess fat. Skim the fat layer from the cooking juices, then return the shredded meat to the slow cooker to absorb the flavorful juices.
05 - Combine green cabbage, red cabbage, grated carrot, and parsley in a large mixing bowl. In a separate small bowl, whisk together mayonnaise, apple cider vinegar, Dijon mustard, sugar, salt, and pepper until smooth. Pour the dressing over the vegetable mixture and toss thoroughly to coat all ingredients evenly. Refrigerate until ready to serve.
06 - Lightly brush the cut sides of the slider buns with melted butter. Toast them in a skillet over medium heat or in a warm oven until golden and slightly crisp, approximately 2-3 minutes.
07 - Pile a generous portion of the moist shredded brisket onto the bottom half of each toasted bun. Top with a spoonful of chilled coleslaw and add pickle slices if desired. Place the bun tops on the slaw and serve immediately while still warm.