Start by combining hoisin sauce, soy sauce, honey, rice vinegar, garlic, ginger, sesame oil, and black pepper in a bowl. Mix until smooth and well blended. I like to taste it at this stage to adjust sweetness or saltiness.
Place the chicken thighs in the slow cooker in a single layer if possible. Pour the prepared sauce over the chicken, making sure each piece is well coated. This helps the flavors soak in evenly as it cooks.
Cover and cook on low for 4–6 hours or high for 2–3 hours. The chicken should become tender enough to pull apart easily. I usually prefer the low setting because it results in juicier meat.
Once cooked, remove the chicken and shred it using two forks or slice it if you prefer larger pieces. Return it to the slow cooker so it can soak up more of that delicious sauce.
If you want a thicker sauce, mix cornstarch with water and stir it into the slow cooker. Let it cook for another 15–20 minutes until the sauce thickens nicely and coats the chicken.
Turn off the heat and sprinkle green onions and sesame seeds on top. This final touch adds freshness and makes the dish visually appealing when serving.