Add remaining ingredients into a food processor or blender. Blend mixture until totally combined and pour over pork loin. Rub mixture over entire surface.
Cover and cook on low 4-5 hours, or on high 3 hours. Pork is done when internal temperature reaches 145˚F.
Remove pork from slow cooker and transfer to a cutting board; cover pork with foil and let rest 15 minutes before slicing.
Meanwhile, add 2 cups romaine lettuce to each individual serving plate and top each salad with 2 tablespoons guacamole. Serve salad alongside sliced pork.