Cut ribs in to pieces depending on the size of your slow cooker. For larger slow cookers, you can usually go with 2 half-slabs.
Add the sliced onion and water to the slow cooker.
Rub salt, pepper and paprika into ribs and place in slow cooker. Cook on low for 8 hours or high for 4 hours. (I like 8 hours on low the best)
After cooking in the slow cooker, coat ribs with barbecue sauce and bake in oven at 375 for about 10-15 minutes. This really sets in the barbecue sauce and caramelizes it slightly for an absolutely awesome flavor.
Remove from oven and add more barbecue sauce if you like and serve.