Pat the pork dry with a paper towel to remove any excess liquid. In a small bowl, combine all 9 spices, from kosher salt through chili powder and stir to combine. Using your hands, rub this mixture all over the pork shoulder. Place a large saute pan on the stove and heat over medium-high heat. Allow the pan to heat properly, then add 1 Tbs canola or vegetable oil. Allow another minute for the oil to heat up, then place the pork in the pan. If your pan is hot enough, it should nicely sear the meat in 2-3 minutes per side. Rotate the pork until all sides are browned. Remove from heat and place in your prepared oven dish or crock pot.
Oven Method: Preheat oven to 275 degrees F. Prepare pork shoulder as instructed above and place in a roasting pan. I usually use some form of a 9 x 13 baking dish with sides about 2-3 inches high. Pour the lime juice over the pork and add the onion and smashed garlic. Cover the pan with foil, sealing all edges. Bake for 5-6 hours, or until internal temperature of pork is at 195 degrees F. Remove from oven and allow roast to sit for 10-15 minutes. Transfer the pork to a cutting board and, using two forks, shred the meat, discarding any fat. Place the meat in a serving dish and pour about ½ cup of liquid from the baking dish back over the meat to help keep the meat slightly moistened and flavorful.
Crock pot method: Turn your crock pot on low or high depending on your cooking time needs. Place the prepared pork in the crock pot. Pour the lime juice over the pork and add the onion and smashed garlic. Place the lid on the crock pot and walk away...seriously, don't open the lid! Here is my opinion on crock pots and cooking large chunks of meat: I always try and cook on low as I feel cooking on high cooks meats way too fast, especially for something that needs a low and slow kinda cook like pork shoulder. Cook on low for 7-8 hours. Cook on high for 4-6. Toward the end of your cook, check the internal temperature of the pork for 195 degrees F and remove from the crock pot once it reaches this temperature. Place on a cutting board and allow to rest for 10-15 minutes. Using two forks, shred the meat, discarding any fat. Place the shredded meat in a serving bowl, covering with approximately ½ cup of liquid from the crock pot to help keep the meat moist and flavorful.