Be sure the coconut oil is in liquid form. If not, place coconut oil in a small saucepan over medium-low heat and cook until melted.
Add peanut butter and cinnamon. Stir until mixture is completely smooth and thoroughly mixed. Mixture should be thick, but pourable.
Pour mixture into tray and freeze until set.
Carefully remove from tray and store in air-tight container in freezer (they soften quickly).
Notes
These were made for dogs in the 10-15 pound range. Adjust the amount coconut oil accordingly. Rule of thumb is that you use 1 teaspoon of coconut oil per 10 pounds of your dog's body weight.