Place boneless pork shoulder in slow cooker with onions surrounding it. If you choose to add our dry rub, mix ingredients and rub over the entire thing before placing in pot.
Pour broth on top and close lid.
Cook on high for 5 hours (for 3.5 lbs.) or low for 8 hours or until meat is fork tender and shreds apart easily with just 2 forks. (if you have to pull it needs more time) Enjoy as is or toss meat with barbecue sauce and enjoy.