Season the beef. Sprinkle 1 teaspoon of seasoned salt over each side of the chuck roast, making sure both sides are evenly seasoned.
Prepare the slow cooker. Set the slow cooker to Low. Arrange most of the sliced onion in an even layer across the bottom, reserving a few slices for the top of the roast.
Brown the chuck roast. Heat the cooking oil in a nonstick skillet over medium-high heat until shimmering. Add the seasoned roast and sear for 3–4 minutes per side, until browned.
Add the beef and cooking liquid. Transfer the browned roast to the slow cooker, placing it over the onions. Pour in the undiluted beef consommé and Worcestershire sauce. Arrange the reserved onion slices over the beef.
Slow cook until tender. Cover and cook on Low for 8–10 hours, or until the roast is very tender and easily pulls apart with a fork.
Shred the beef. Carefully transfer the cooked roast to a cutting board. Use two forks to shred the meat, removing and discarding any excess fat and tough membranes.
Keep the beef warm. Return the shredded beef to the slow cooker and gently mix it with the cooking juices. Keep warm while preparing the buns.
Toast the slider buns. Melt the butter in a nonstick skillet over medium heat. Open the slider buns and place them cut-side down in the skillet. Toast for 2–3 minutes, until lightly golden. Repeat with the remaining buns, adding more butter if needed.
Assemble the sliders. Place a half-slice of provolone cheese on each bun half. Add approximately ⅓ cup shredded beef to each bottom bun, squeezing out most of the cooking liquid first. Top with cooked onions, as desired.
Serve warm. Place the top buns over the filling and serve while the beef is warm and the cheese is softened.