Combine pineapple, garlic, cumin, salt, red pepper flakes, and pepper in a bowl.

Place pork roast into a slow cooker. Pour pineapple mixture over top. Cover and cook on Low until pork is slightly pink in the center and cooked through, about 8 hours. An instant-read thermometer inserted into the center should read at least 145 degrees F (63 degrees C).

Remove pork roast from the slow cooker. Cut away any fat, then shred meat using two forks. Return meat to the slow cooker and mix with the juices.