Use paper towels to blot the pork dry, which helps the spices cling and limits surplus moisture.
Whisk brown sugar, paprika, garlic powder, onion powder, salt, pepper, and cumin together in a small bowl until the blend is even and consistent in color.
Work the spice blend over every surface of the pork; press gently with your hands so the flavors cling and soak in throughout slow cooking.
Layer the sliced onion across the Crock Pot bottom, forming a savory base that also guards against sticking.
Slowly add chicken broth (or water) around the pork without rinsing off the seasoning; this liquid keeps the meat moist through low and slow cooking.
Set the lid on and cook on LOW for 8 hours, leaving the lid in place; this breaks down collagen for a tender, melt-in-your-mouth texture.
Transfer the pork carefully to a large tray; pull it apart with two forks into fine strips (it will fall apart easily); discard any large fat pieces if needed.
Stir BBQ sauce into the shredded pork until every strand is coated; for a thicker sauce, warm it in a skillet before mixing.
Serve hot right away; enjoy on soft brioche buns, in corn tortillas for tacos, or with sides like coleslaw, potatoes, or freshly baked bread.
