Cut onions into 4 rings each, place at the bottom of the slow cooker.
Mix together spices and salt and rub into pork.
Place pork on top of onions and pour tangy barbecue sauce on top and water around the sides.
Cook on low 8 hours.
MAKE THE COLESLAW
In a large bowl, mix together mayonnaise, vinegar, sugar, mustard, and salt.
Add coleslaw mix to the mayo mixture and stir using a spatula until well combined.
Refrigerate for at least 30 minutes, serve chilled.
Finish & Assemble
Remove meat and onions from the slow cooker and dispose of liquid. Shred meat and remove bone. Add meat back to the slow cooker with as much of the onions as you would like. Add 1/2 barbecue sauce and stir to combine. Keep warm until ready to serve.
Assemble sliders with meat, extra barbecue sauce, and coleslaw.