In a food processor or blender, blend together sauce ingredients (onion, garlic, chipotles, green chilies, lime juice, apple cider vinegar, ground cumin, oregano, 2 tsp salt and 2 tsp black pepper with 1 cup of beef broth.
Pour mixture into bottom of crockpot.
in a large skillet heat 2 TBS cooking oil on medium high heat. Season top of roast with salt & pepper. Place roast season side down in hot oil, season with salt and pepper. Sear meat for 4-5 minutes until browned. Turn roast over and sear on that side for an additional 4-5 minutes.
Submerge roast into liquid sauce in crockpot. Cook roast for 8-9 hours on low or 6-8 hours on high. The time will depend on how thick the roast is. You will want to make sure the roast is cooked through and very tender.
Shred roast with 2 forks and let sit in the juices of crockpot.
Serve making Birria Tacos (I have a recipe for this, just search recipe bar at top of page.), also serve over rice bowl with corn, beans, cilantro, tomatoes, sour cream, and cheese. Enjoy.