In a medium bowl, whisk together the tamari, crushed pineapple, tomato paste, honey, garlic powder, onion powder, ginger and salt. Scoop ¼ cup of the mixture and set aside.
Add the chicken to a 6-qt slow cooker. Add the remaining sauce, turning the chicken to coat.
Cover and cook on high for 4 hours or low for 6.
Uncover and shred the chicken with 2 forks. Add the remaining ¼ cup sauce, stirring to combine. Taste and add additional salt if desired.
Serve the chicken warm on buns, in bowls, or in lettuce wraps with Creamy Cabbage Slaw, if desired.