Start by preparing your roast. Trim all of the visible fat from the roast. Pat the exterior of the roast dry. Cut your roast into about 8 equal sized chunks. Sprinkle half of the salt on the top of the chunks of roast and set aside.
In a blender combine apple cider vinegar, garlic, cumin, oregano, black pepper, smoked paprika, cloves, chipotle peppers, adobo sauce, broth, and lime juice. Blend well until smooth and set aside.
Warm a cast iron dutch oven over medium high heat. Add olive oil to the pan and place the chunks of roast, salt side down in. Sprinkle the exposed side with the remaining salt and sear each side of the roast well to develop a good crust.
Either turn your crock pot to low or transfer the beef from the searing pan to a crock pot that is warmed to low. Pour the sauce you made over the top of the roast and move the pieces of roast around. Cook on low for 7 hours.
After 7 hours, shred your roast and place it back in the crock pot. Cook for another hour on low.
Serving as Tacos:
Grill double stacked corn tortillas. Place a generous portion of the barbacoa in the center of the shell. Top with arugula and queso fresco.