Remove the seeds and stems from the chilies. Set aside.
Quarter the onion, then peel and smash the garlic.
In a large skillet with tall sides, heat the avocado oil over medium heat. Add the onion, garlic, diced tomatoes, and 1 chipotle in adobo sauce; cook for 5-10 minutes.
In a small pot (on a separate burner), bring the water or broth to a boil. Add the dried chilies and reduce heat to a simmer for 10 minutes.
Add in the cumin, ginger, bay leaf, cinnamon, clove, thyme, oregano, salt, and pepper to the large skillet.
Pour the cooked pot of chilies into the large skillet and mix, cooking for another 10 minutes.
Remove the large skillet from heat and let cool for 5-10 minutes.
Carefully transfer the mixture into a blender. It will still be hot, so do not totally seal the lid and be sure to cover it with a towel! Blend until smooth; it will be thick.
Generously salt (using about 1 tablespoon) all sides of the meat and place it in the slow cooker.
Using a fine strainer or cheesecloth, strain the birria sauce mixture into the slow cooker over the meat. It helps to press the sauce with a spoon to get as much of the flavorful broth in as possible!
Cook on low for 4-6 hours, checking the meat to make sure it's done.
Once the meat is cooked, separate the beef and broth, remove and discard the bones, then shred the meat.
Combine the shredded meat with the broth again and enjoy any way you want or save for later!