01 - Preheat oven to 350°F. Slice slider buns horizontally if not pre-sliced.
02 - Place bottom halves of buns on a parchment paper-lined baking tray.
03 - Distribute corned beef evenly over buns. Top each with half a slice of Swiss cheese if using.
04 - Place one dill pickle slice on each slider.
05 - Spread mustard generously on top bun halves and place atop sliders to close.
06 - Whisk melted butter with garlic powder and poppy seeds until combined. Brush mixture over bun tops.
07 - Cover tray loosely with foil. Bake for 8–10 minutes until cheese melts and sliders are heated through.
08 - Remove from oven, uncover, and serve warm.