Cut ribs into smaller chunks. Place on a cookie sheet lined with tin foil (helps with cleanup). Sprinkle both sides with salt and pepper, then broil in the oven for 15 minutes, flipping them halfway through. When they're brown and starting to crisp, place them in layers in the crock pot with sliced onion and BBQ sauce. Cook for 8 hours on low or 4 hours on high.
You can brown your ribs and fill the crock pot the night before and refrigerate overnight, then just throw it on in the morning. It doesn't get much easier than that!