Pat the roast dry and season it with salt and pepper. Heat the oil in a large skillet and sear the roast to get a nice brown crust on the outside of the roast. Set the meat into the slow cooker.
Saute the onion, celery, and garlic in the remaining oil in the skillet until browned, 3-4 minutes. Add them to the slow cooker.
Warm the broth in the skillet and add the broth to the meat and vegetables.
Wipe the skillet with a paper towel and remove the stems and seeds from the dried chilis. Give them a rinse inside to dislodge any dust or dried insects or spiders (yes, it happens.)
Toast the chilis in a dry skillet until just starting to brown, 1-2 minutes. Watch as they can burn and if they burn they'll make your broth taste bitter. Then, add the chilis to a small saucepan, cover them with water, and bring them to a low simmer. Simmer for 5 minutes, then drain and add the chilis to the crock pot.
Add the cider vinegar, cumin, and oregano to the slow cooker and pop the lid on.
Set the slow cooker on high and cook for 4-5 hours or on low for 7-8.
At the end of the cooking time, remove the beef and set aside until cool enough to handle, then shred it using two forks or meat claws.
Strain the broth and discard the solids. Season the broth with additinoal salt and pepper, if necessary.
Serve portions of the beef along with the broth (consomme) in bowls and garnish with onion, cilantro, avocado, jalapenos, lime wedges, and your favorite toppings.