Preheat oven to 325℉ or preheat slow cooker if using a smaller shoulder. Whisk together the pork "sauce" ingredients in a medium bowl (liquid smoke, hoisin, soy sauce, rice vinegar, crushed pineapple, pineapple preserves, garlic powder, and black pepper).
Add pork shoulder to large pot/dutch oven or slow cooker and pour over the sauce mixture. Cover and cook for 5 hours in the oven, 4-5 hours for a smaller shoulder on low in the slow cooker, or 8-10 hours on high. (I turned my pork shoulder over halfway through cooking and ladled some of the cooking liquids over the pork to help it stay juicy throughout the cooking process.)
To make the slaw, combine all slaw ingredients in a medium bowl and toss to combine. Season to taste with salt.
Once pork is done, remove from oven/slow-cooker and let cool for 15 minutes or so. Shred with two forks and add to a large bowl. Pour all of the cooking liquid over the pork and toss to let it soak in. Serve the pork in grilled tortillas topped with slaw, a sprinkle of chopped scallions, and some fresh chopped pineapple!
If you want to use a smaller 4-5 lb. pork shoulder, you can cook it in the slow cooker instead. I'd cook it 4-5 hours on high, or 8-10 on low.