Pat the chicken thighs dry with paper towels.
Season both sides of the chicken with the salt, pepper, garlic powder, and smoked paprika.
Heat the oil in a large skillet over medium-high heat.
Sear the chicken thighs skin-side down for 4–5 minutes until deeply golden. Flip and cook for another 2 minutes.
Transfer the chicken to a 6-quart slow cooker, skin-side up.
In a medium bowl, whisk together the cranberry sauce, barbecue sauce, brown sugar, Dijon mustard, apple cider vinegar, Worcestershire sauce, onion powder, and thyme until well combined.
Pour the sauce around and over the chicken.
Cover and cook on LOW for 5–6 hours or HIGH for 3–4 hours, until the chicken is tender and reaches an internal temperature of 165°F.
Carefully transfer the chicken to a platter and loosely tent with foil.
In a small bowl, whisk together the cornstarch and cold water until smooth.
Stir the cornstarch slurry into the sauce in the slow cooker.
Turn the slow cooker to HIGH, leave the lid slightly ajar, and cook for 15–20 minutes, stirring occasionally, until the sauce thickens into a glossy glaze.
Return the chicken to the slow cooker and spoon the thickened glaze generously over each piece.
Sprinkle with chopped parsley before serving.