Peel the onion and slice into thick slices. Wash and slice the orange and lime into thick slices. Layer the onion and citrus slices along the bottom of a 6-quart slow cooker.
Stir together the salt, cumin, oregano, garlic powder, pepper and cayenne.
Place the pork on top of the onion and citrus slices. Sprinkle evenly with the seasoning mixture.
Cook on LOW for 8 - 10 hours.
Remove the pork and shred with two forks. Remove any visible fat.
Strain the liquid. Return the shredded pork to the slow cooker and pour the drained liquid over the shredded pork. Set the slow cooker to low heat and cover.
Preheat oven to 350 degrees.
Slice the slider buns in half. Place on a sheet pan lined with parchment paper.
Place six slices of Swiss cheese on the bottom half of the slider buns. Top with six slices of ham. Top with half of the slow cooked pork. Reserve the other half of the pork for another meal - or double the slider recipe.
Top the pork with the 12 pickle slices (one per slider) and drizzle evenly with yellow mustard. Top with the remaining six slices of Swiss cheese. Place the top half of the buns on top of the cheese.
Melt the butter and brush over the tops of the sandwiches.
Cover with foil and bake for 20 minutes. Slice and serve.