Cut the roast into 4 or 5 steaks, dust with a rub, sear off on the bbq. Let cool.
Whiz the marinade together in a small food processor and place in a large ziploc bag. Place the steaks into the bag and massage the rub in. Place in fridge overnight.
Place the steaks in the crockpot along with any remaining marinade. I mixed the beef broth with the sauce at this point, layering in the steaks, coating in the sauce, covering as best as possible.
Cook on low for about 8 hours.
Scoop out the liquid into a saucepot, skimming off any fat, bring to a boil to thicken.
Take the meat out and shred if needed (mine just fell apart being scooped out of the crockpot), add as much sauce as desired, mixing so its all coated.