Place the pork roast in your slow cooker.
In a small bowl, whisk together the Chinese five spice, 2 tablespoons of brown sugar, garlic powder, 1 teaspoon crushed red pepper, 1 teaspoon salt, and 1/2 teaspoon black pepper.
Rub the spice mixture all over the pork roast (including the bottom). Pour 1 cup of water around the side of the pork roast. Try not to pour it over top. Cover and cook on low for 8 hours or high for 4 hours. When there is about 20 minutes left on the cooking time, prepare your glaze.
In a small bowl, mix together the cornstarch and 2 tablespoons of cold water until dissolved. Set aside.
To a large saucepan, add 1/2 cup of the remaining cold water, apple cider vinegar, soy sauce, 1 teaspoon crushed red pepper, and 3/4 cup brown sugar. Bring to a simmer and then stir in the cornstarch mixture. Continue to stir until the glaze has thickened, about 5 minutes. Remove from heat.
Remove the pork from the slow cooker and discard the liquid. Generously brush the pork with the glaze while the pork is still hot. Serve the remaining glaze on the side.
Serve the pork with chopped fresh cilantro and lime wedges. Enjoy!