Prepare the chicken: Place the chicken breasts in the slow cooker.
Make the sauce: In a small bowl, whisk together sweet chili sauce, soy sauce, honey, rice vinegar, garlic powder, ground ginger, and red pepper flakes (if using).
Cook the chicken: Pour the sauce mixture over the chicken breasts. Cover and cook on low for 6-7 hours or on high for 3-4 hours, until the chicken is tender and easily shreds.
Shred the chicken: Once the chicken is fully cooked, shred it using two forks and mix it into the sauce.
Garnish and serve: Garnish with sesame seeds, green onions, and cilantro before serving.