Add chicken, BBQ sauce, and sliced onions to crockpot and cook on HIGH for 3.5 hours, or LOW for 7 hours {covered}, or until done.
After chicken is cooked, remove from crockpot and shred using 2 forks.
Place a nice sized portion on the bottom bun of your sandwich, drizzle with a little extra sauce from the crockpot, and top with Crispy Bacon slices and top bun. YUM!