Spray a 13x9x2-inch casserole dish with cooking spray and layer noodles on the bottom. Build the casserole in layers on top of the noodles: ⅓ of the chicken mixture, a layer of noodles, ½ of the spinach, a layer of noodles, ⅓ of the chicken mixture, a layer of noodles, the remaining /12 of the spinach, a layer of noodles, and the remaining ⅓ of the chicken mixture. Spread the mozzarella cheese over the top.