1. Mix all dry rub ingredients together.
2. Rub the entire roast with the dry rub (you should use it all.)
3. Place a layer of onions on the bottom of your slow cooker.
4. Place the roast on top. Put the rest of the sliced onions on top of the slow cooker. NO LIQUID NECESSARY!
5. Cook the roast on high for 5-6 hours and then turn down to low for another 3-4 hours or until the roast is literally falling apart and easy to shred.