Preheat your oven to 180°C (350°F). Slice the buns horizontally, keeping the top attached, and place the bottom half in your baking dish.
Spread a thin layer of smoky BBQ sauce evenly over the cut side of the bottom bun. This adds a tangy, smoky flavor that permeates the sandwich.
Layer the honey-glazed ham slices over the sauced bun, arranging them evenly so every bite gets that savory, sweet flavor.
Add a layer of thinly sliced caramelized onions on top of the ham for a sweet, melt-in-your-mouth contrast. If you're using cheese, place slices over the onions now.
Brush the cut sides of the top bun with melted butter mixed with garlic powder for a shiny, flavorful finish.
Gently place the top bun over the assembled layers, pressing down lightly to help everything meld together.
Bake uncovered in the preheated oven for 10-12 minutes, until the cheese is bubbly and the buns are golden around the edges.
Remove from oven and let sit for 3-5 minutes to allow the flavors to settle and the juices to redistribute.
Slice into individual sliders if desired, then serve warm, optionally with extra BBQ sauce or pickles on the side.