Pat the pork shoulder dry with paper towels on all sides.
In a small bowl, mix together the brown sugar, paprika, garlic powder, onion powder, salt, pepper, and cumin until evenly combined.
Rub the spice mixture all over the pork, pressing firmly so it adheres to every surface.
Heat 1 tablespoon of vegetable oil in a large skillet over medium-high heat. Sear the pork for 2-3 minutes on each side until golden brown. (Optional but highly recommended.)
Place the sliced onion in an even layer at the bottom of the Crock Pot.
Set the pork shoulder on top of the onions. Pour the chicken broth around the sides of the pork, being careful not to pour it directly over the spice rub.
Cover and cook on LOW for 8 hours. Do not lift the lid during cooking.
Once cooked, remove the pork and place it on a large cutting board or tray. Use two forks to shred the meat into fine strands, discarding any large pieces of fat.
Add the BBQ sauce to the shredded pork and mix until every strand is fully coated. For a thicker sauce, warm the BBQ sauce in a skillet before mixing.
Serve hot on brioche buns, in tacos, over rice, or as sliders. Enjoy!