01 - In a small bowl, whisk together soy sauce, brown sugar, hoisin sauce, chicken broth, rice vinegar, sesame oil, cornstarch, garlic, ginger, and red pepper flakes until smooth and well combined.
02 - Place chicken thighs in an even layer at the bottom of the slow cooker, ensuring pieces are not overcrowded.
03 - Pour the prepared sauce mixture over the chicken, turning pieces to coat thoroughly and evenly distribute the sauce.
04 - Cover and cook on low heat for 4 hours until chicken is tender, reaches an internal temperature of 165°F, and easily shreds with a fork.
05 - Remove cooked chicken from the slow cooker and shred into large bite-sized pieces using two forks. Return shredded chicken to the pot and stir well to coat with sauce.
06 - Plate hot Mongolian chicken over steamed jasmine rice or noodles, generously garnished with sliced green onions and toasted sesame seeds.