Place onion in the slow cooker. Add the garlic. Whisk the cumin, salt, pepper, oregano, and red pepper flakes. Rub liberally all over pork. Nestle the pork into the slow cooker.
Whisk the chicken broth and lime juice together and add to the slow cooker. Cover and cook on low for 8 to 9 hours until the pork shreds easily with a fork.
Remove the pork from the slow cooker and place in a bowl. Shred with two forks. Put pork back in the slow cooker and stir to mix in the juices.
Meanwhile, preheat broiler. Combine the mayo and mustard in a small bowl. Spread evenly over the tops of the slider buns arranging the bottoms on a baking sheet as you work. Spoon heaping portions of the pork into the buns and top with ham and Swiss cheese. Broil for a minute or two, just to melt the cheese.
Top with a pickle and the mayo-mustard coated bun tops. Serve.