Slice each slider bun in half and place the bottoms in a baking dish. Layer 2 to 3 slices of ham on each bun, folding to fit. Layer the cheese slices over the ham, trimming any excess.
Spoon ½ tablespoon of mustard onto each top bun, then add top buns to the sliders.
Brush each bun with a thin layer of water and sprinkle with pretzel salt. Place in the oven and bake for 15 minutes, or until the cheese is melted.
Remove the sliders from the oven and serve immediately.