Prep the roast: Pat the chuck roast dry and season lightly with salt and pepper. This helps build flavor before the seasonings go on.

Layer in the slow cooker: Place sliced onions on the bottom if using. Add the roast on top. Sprinkle ranch seasoning and au jus mix evenly over the meat. Add the stick of butter, pepperoncini, and 1–2 tablespoons of pepperoncini brine.

Cook until tender: Cover and cook on Low for 8–9 hours or on High for 4–5 hours, until the roast shreds easily with two forks.

Shred and skim: Remove the roast to a cutting board and shred. Skim excess fat from the cooking liquid. Return the shredded meat to the slow cooker and stir so it absorbs the juices. Taste and adjust salt and pepper.

Prep the rolls: Heat the oven to 350°F (175°C). Slice the slider rolls in half horizontally, keeping the tops together and bottoms together. Place the bottom half on a parchment-lined baking sheet.

Add sauces (optional): Stir mayonnaise and Dijon together and spread a thin layer over the bottom rolls for extra moisture and tang.

Layer the sliders: Add a layer of cheese slices to the bottom rolls. Spoon a generous amount of shredded pot roast over the cheese, letting some juices drip but not flood. Top with more cheese if you like. Place the top rolls on.

Brush and bake: Mix melted butter with Worcestershire and a pinch of ranch seasoning if you have extra. Brush over the tops of the rolls. Sprinkle with poppy seeds or sesame seeds.

Bake to finish: Cover loosely with foil and bake for 12–15 minutes, until the cheese is melty. Uncover and bake 3–5 minutes more to lightly crisp the tops.

Slice and serve: Let rest for 5 minutes, then cut into individual sliders with a serrated knife. Serve warm with extra pepperoncini on the side.