Trim excess fat from pork shoulder and also cut deep slits into the meat.
Place largefrying pan on high heat, pour oil in pan and brown meat on all sides.
Once browned on all sides transfer the pork shoulder to the slow cooker.
Mix all ingredients for wet spice rub and brush all over pork shoulder, including in the slits (this will make sure the meat inside the shoulder will also be coated in the spice rub).
Place the remaining ingredients into the slow cooker (chopped onion, jalapeno, tomato paste, soy sauce, brown sugar, cumin, oregano, salt, chili powder, garlic powder, onion powder, smoked paprika, pepper).
Cook on low for 6-8 hours.
Transfer pork to a large baking pan and shred with 2 forks.
Strain the juices from the slow cooker pot into a measuring cup and pour over the shredded meat.
Broil the meat until golden brown and crispy on the edges. Stir the meat a few times until most of the pieces are browned and crispy.
Serve with flour tortillas, guacamole, salsa, queso cheese, cilantro etc.
Store any leftover meat in a Shape+Store freezer container.