In a small bowl, mix together the salt, garlic powder, cumin, chili powder, oregano, coriander, and cinnamon.
Rub the spice mixture all over the pork chunks to coat evenly.
Place the pork in the bottom of a slow cooker. Pour the chicken broth and orange juice around the sides (not over the top) to avoid rinsing off the spice coating.
Cover and cook on low for 10 hours, or until the pork is very tender and shreds easily with a fork. (Alternatively, cook on high for 5–6 hours.)
Once pork is fully cooked, preheat the oven to broil and line a large baking sheet with aluminum foil.
Remove pork from the slow cooker and use a fork to shred the meat into bite-sized pieces. Transfer the pork to the baking sheet in an even layer. (Reserve the juices in the slow cooker for the next step.)
Place the baking sheet under the broiler for about 5 minutes, or until the edges of the pork begin to brown and crisp.
Remove the sheet from the oven, ladle about ¼ cup of the reserved juices over the pork, and toss to coat. Return to the broiler for another 5 minutes, until the pork is crisp and golden.
Remove from the oven and ladle another ¼ cup of the juices over the pork for added moisture and flavor.
Serve immediately in tacos, nachos, or salads. Garnish with chopped cilantro, if using.