In a bowl, whisk together soy sauce, brown sugar, honey, rice vinegar, minced garlic, grated ginger, and sesame oil until sugar is mostly dissolved.
Place chicken breasts in the bottom of the crock-pot and pour the teriyaki sauce over them, turning the chicken to coat.
Cover and cook on LOW for 4 hours or until the chicken is cooked through and tender.
Remove the chicken to a cutting board and shred or slice as desired. Pour remaining sauce from the crock-pot into a saucepan.
Whisk cornstarch into cold water to make a slurry. Bring the sauce to a simmer and whisk in the slurry, cooking until the sauce thickens, about 1–2 minutes.
Return the shredded chicken to the sauce to coat, or spoon the sauce over the chicken when serving. Serve over steamed rice and garnish with sliced green onions and sesame seeds.
Notes
Leftovers keep in an airtight container in the refrigerator for up to 3 days. Reheat gently and add a splash of water if the sauce thickens too much.