Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Peel the carrots and slice them into 1/2-inch thick rounds or diagonal coins for maximum surface area.
In a small bowl, whisk together the maple syrup, olive oil, apple cider vinegar, half of the salt, half of the pepper, and the fresh thyme.
Toss the sliced carrots in half of the maple glaze mixture until well coated, then spread them out on one side of the prepared baking sheet.
Season the chicken breast with the remaining salt and pepper, brush with the rest of the glaze, and place it on the other side of the baking sheet.
Roast for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the carrots are tender with caramelized edges.
Place the fresh baby spinach on a plate and top with the hot chicken and carrots, allowing the greens to wilt slightly from the residual heat before serving.