MAKE THE RUB In a small bowl, combine the salt, pepper, cumin, oregano, chili powder, and garlic powder. Set aside.
MAKE THE PORK In a separate bowl, whisk together the broth, orange juice, lime juice, apple cider vinegar, and garlic. Set aside.
Cut the pork shoulder into 3 equal chunks. Pat dry, then rub with the spice mixture on all sides until it is evenly and generously coated.
Heat the olive oil in a large skillet, preferably cast-iron, over high heat until it shimmers. Add the pork pieces and sear on all sides, until a deep brown color forms, 2 to 3 minutes per side.
Transfer the browned pork to a slow cooker.
Reduce the heat in the skillet to medium and cook the onion, stirring, until slightly softened, about 2 minutes.
Transfer the cooked onion to the slow cooker and nestle them around the pork. Pour in the broth mixture and add the bay leaves. Cover and cook on High for 4 to 6 hours or on Low for 8 to 10 hours, until the pork is fall-apart fork-tender.
When ready to eat, turn the broiler on (set to high if you have the option). If you don't have a broiler, heat the oven to 500°F or as hot as you can get it.
Use tongs to transfer the pork to a large rimmed baking sheet.
Discard the bay leaves. Do not dispose of the liquid remaining in the slow cooker; reserve it for later. Using two forks, shred the pork and spread it in a single even layer over the baking sheet.
Place the pork under the broiler or in the oven and cook until the pork begins to crisp up on the edges, 3 to 5 minutes, depending on how hot your broiler gets. Remove from the oven and pour ¾ cup of the reserved cooking liquid all over the pork. Use tongs to toss everything together and again spread the pork into a single layer. Return to the oven and cook until the edges are crisp, 3 to 5 more minutes. Watch carefully as it crisps to make sure it doesn't burn.
Pour an additional ½ cup of the reserved cooking liquid over the pork and give it one last toss to coat evenly.
Serve with the diced onion, cilantro, avocado, lime wedges, and hot sauce.