Prep the chicken: Trim excess fat. If using bone-in skin-on thighs, you can sear them skin-side down in a skillet for 3–4 minutes to render some fat and boost flavor. This step is optional.
Make the sauce: In a bowl, whisk honey, soy sauce, ketchup, rice vinegar, hoisin (if using), garlic, ginger, sriracha/chili flakes, black pepper, sesame oil, and broth until smooth.
Load the crockpot: Place the chicken in the slow cooker in a single layer if possible.
Pour the sauce over the top, making sure each piece is coated.
Cook: Cover and cook on Low for 4–5 hours or High for 2.5–3 hours, until the chicken is tender and reaches 165°F internally. Avoid lifting the lid too often.
Thicken the sauce: Transfer the cooked chicken to a plate. Ladle the cooking liquid into a saucepan (or leave it in the crockpot if yours simmers).
Bring to a gentle simmer. Stir in the cornstarch slurry and cook 1–3 minutes until glossy and thick enough to coat a spoon.
Glaze the chicken: Return chicken to the sauce and gently toss to coat. Let it sit a couple of minutes so the glaze clings.
Garnish and serve: Sprinkle with sesame seeds and green onions.
Serve over rice, spooning extra sauce on top.