Season the ribs with salt and pepper on both sides and cut them in half to fit inside the slow cooker.
Pour ½ cup water into the slow cooker and place the ribs inside with the sliced onions and minced garlic over them. Put the lid on and cook on high for 4 hours.
Preheat the oven to 375F. Take the ribs out of the slow cooker carefully, they will be very tender! Place them on a baking sheet and brush them with barbecue sauce. Bake them for 10-15 mins until the sauce caramelizes.