Rinse the ribs to make sure there are no bone shards and trim visible fat. Pat them dry with a paper towel.
If desired, remove the back membrane off the ribs by using a pairing knife to gently slide under the membrane and pry it up. You'll be glad you did this. It is worth the effort. As the skin lifts I shove my finger underneath. Use a paper towel to grab a hold of the membrane and pull it off. As the skin lifts up more you pull it towards the other end of the rack. Almost like pulling off a band aid, very, very slowly.
Throw the membrane away. I find it easier to cut my rib racks in half to cook them. It is up to you. Trim any visible fat from your ribs. Rinse and pat dry.
Once membrane removed, cut the ribs in half, if desired.
Place the brown sugar, paprika, salt, pepper, garlic powder, and onion powder in a small bowl. Mix to combine.
Rub the spices evenly all over both sides of the ribs. We use our hands to do this. It might like seem like a lot of seasoning, but you should use all of it. Allow ribs to sit for 30 minutes to come to room temperature covered in rub.
Spray the slow cooker and/or insert with cooking spray. Place the ribs, covered with rub, in the slow cooker, around the edges first if possible. You can add some BBQ sauce on top if you want. Slow cook for 4-5 hours on high or 6-8 hours on low.
Exact cooking time will vary depending on your slow cooker and the thickness of your ribs. We remove the ribs once we notice that the meat has shrunk back on each rib bone, about a half an inch.
Place the broiler setting on high. Carefully remove the ribs from the slow cooker, they will be extremely tender.
Place the ribs on a rimmed baking sheet covered in tinfoil for easy cleanup, if desired. Brush the bbq sauce generously all over the ribs. Carefully broil under your broiler until lightly charred and you begin to see lots of tiny bubbles all over the surface of your ribs. You can baste again with more sauce and let it bubble again to caramelize the sauce some more if desired. We generally do.
Serve immediately while ribs are hot