Heat the oven to 350 °F, then line a 9x9-inch or 9x13-inch pan with aluminum foil and coat it with cooking spray. The lined pan makes cleanup easier and helps the sliders release cleanly after baking.

Use a large serrated knife to cut the entire package of rolls horizontally into one connected top slab and one connected bottom slab. Keeping the rolls attached gives you the classic pull-apart shape and makes layering much easier.

Set the bottom slab into the prepared pan and spread half of the ham evenly over the cut surface. A flat first layer helps support the cheese so the sliders stay stacked instead of shifting around.

Add the Swiss cheese in an even layer, then cover it with the remaining ham. The ham cheese ham order helps the filling stay stable and keeps the cheese tucked into the middle where it melts best.

Place the top slab of rolls over the filling and press very lightly to settle everything into place. The slab should look even and compact, not squashed.

Put the butter in a medium microwave-safe bowl and heat it on high power until melted, about 1 minute. You want fully melted butter so the seasonings whisk in smoothly.

Whisk the Dijon mustard, poppy seeds, dried minced onion, Worcestershire sauce, salt, and pepper into the butter until well combined. The glaze should look speckled and glossy, with the onion and seeds suspended throughout.

Pour the butter mixture slowly over the tops of the rolls and spread it across the surface with a spatula. Some of the glaze should pool lightly around the base of the rolls, which helps the bread absorb flavor as it rests.

Cover the pan with aluminum foil and let the assembled sliders stand at room temperature for 5 to 10 minutes. This short rest is important because the glaze sinks into the tops and the rolls start to smell buttery and savory before they even bake.

Bake the covered sliders for about 20 minutes. When ready for the next step, the cheese should be fully melted and starting to bubble inside the layers.

Remove the foil and continue baking for about 3 to 5 minutes, watching closely. The tops should turn golden brown with a slight bounce when tapped, and the toasted onion aroma will really bloom.

Slice the sliders into individual portions and serve right away while warm. The best texture is fresh from the pan, when the cheese is stretchy and the tops are still lightly crisp.