Prepare the Chicken
Trim any excess fat from the chicken thighs or breasts. If using large pieces, cut them into smaller portions.
Make the Sauce
In a bowl, whisk together soy sauce, brown sugar, honey, garlic, ginger, rice vinegar, water, and sesame oil until well combined.
Assemble the Slow Cooker
Place the chicken in the bottom of your slow cooker in a single layer.
Pour the teriyaki sauce evenly over the chicken, ensuring each piece is well coated.
Cook the Chicken
Cover the slow cooker and cook on low for 6–7 hours or high for 3–4 hours, until the chicken is tender and cooked through (internal temperature of 165°F).
Thicken the Sauce
About 30 minutes before serving, remove the chicken from the slow cooker and set it aside.
Mix the cornstarch with 2 tablespoons of water to create a slurry, then stir it into the sauce in the slow cooker.
Turn the slow cooker to high and let the sauce thicken for 20–30 minutes.
Combine and Serve
Return the chicken to the slow cooker and toss it in the thickened sauce.
Serve the chicken over steamed rice or noodles, and garnish with green onions and sesame seeds.