Season thighs with salt and pepper and place them skin-side up in the crockpot.
Whisk orange juice, soy sauce, brown sugar, rice vinegar, ginger, garlic, and sesame oil; pour over the chicken.
Cook on low for 6 hours (or high for 3.5–4 hours) until thighs are tender.
Remove thighs to a plate and skim fat if needed; stir cornstarch slurry into the sauce and cook on high 10–15 minutes to thicken.
Return thighs to the sauce to coat, sprinkle with orange zest, green onions, and sesame seeds.
Serve over rice or noodles; shred extras for sandwiches or bowls.