Place pork roast, blueberries, chili sauce, vinegar, onion, garlic, pineapple, pepper flakes, salt, and pepper in a 4-quart slow cooker. Cook on Low until pork is slightly pink in the center, 8 to 10 hours. An instant-read thermometer inserted into the center should read at least 145 degrees F (63 degrees C).
Transfer pork to a plate and shred with 2 forks. Mash the contents of the slow cooker with a potato masher until fairly smooth. Return shredded pork to the slow cooker and toss to coat in the sauce.
