Preheat the oven to 400°F (200°C).
Add the apple juice, maple syrup, and dried thyme to a small saucepan. Bring the mixture to a gentle boil, then reduce the heat and simmer for about 5–6 minutes, or until the liquid has reduced by approximately half and thickened slightly. Remove from the heat.
Season the chicken thighs on both sides with salt, black pepper, and ground sage.
Heat a cast-iron or oven-safe skillet over high heat. Add the chicken thighs and sear for 2–3 minutes per side, until nicely browned.
Remove the pan from the heat. Arrange the sliced apples, cranberries, and fresh thyme sprigs around the chicken.
Divide the maple sauce in half. Brush half of the sauce generously over the chicken thighs.
Transfer the skillet to the preheated oven and bake for 35–45 minutes, or until the chicken reaches an internal temperature of 165°F (74°C) at the thickest part.
Remove the pan from the oven and let the chicken rest briefly. Serve with the remaining maple sauce spooned over the chicken or on the side.