for serving: cilantro, red onions, tortillas and lime wedges
Cut the chuck roast into large chunks, removing any excess fat. Generously season all sides of the meat with sea salt and black pepper.
Heat a large skillet over medium-high heat. Add the meat and sear on all sides.
Place the meat and all other ingredients in a slow cooker. Mix together to coat the meat with all the herbs and spices.
Cover and cook on low for 8 hours, or on high for 4-5 hours. When tender, shred the meat by pulling it apart with a fork. Taste and season with more salt as needed.
Serve barbacoa in warm corn tortillas with chopped red onions, cilantro and lime juice.
To make in the Instant Pot: Use the Sauté setting on the Instant Pot to sear the meat on all sides. Once browned, press Cancel to turn off the heat. Add the remaining ingredients to the Instant Pot, close the lid and seal the vent valve. Then press Manual, set to High Pressure and cook for 60 minutes. Turn the vent valve to release pressure, open the lid and shred meat with a fork.