Place onions into the bottom of a slow cooker and scatter garlic over top. Set pot roast in the cooker and season with pepper and salt. Pour BBQ sauce over pot roast, making sure roast, onions, and garlic are completely covered. Drizzle honey over roast only.
Cover and cook until meat is easily shredded with 2 forks, on Low for about 12 hours or High for about 6 hours.