01 - Preheat oven to 350°F. Slice slider buns horizontally if not pre-sliced.
02 - Place bottom halves of buns on a baking tray lined with parchment paper.
03 - Layer corned beef evenly over the buns. If using, place half a slice of Swiss cheese on each.
04 - Add a slice of dill pickle to each slider.
05 - Spread a generous amount of mustard on the top halves of the buns, then place them on top to assemble the sliders.
06 - Mix melted butter with garlic powder and poppy seeds. Brush the tops of the buns with the mixture.
07 - Cover the tray loosely with foil and bake for 8–10 minutes, until the cheese melts and the sliders are heated through.
08 - Remove from oven, uncover, and serve warm.