Place 2 cups of the oats in a food processor and grind until it has a flour-like consistency. Place the ground oats in the large mixing bowl.
To the mixing bowl, add the remaining 1 cup of whole oats, peanut butter, cinnamon, flax seed if using, and honey or water. Mix to combine. Add additional oats if the mixture is too wet, and banana, peanut butter, honey or water if it is too dry. You want the dough to hold together but not be sticky or wet.
Preheat oven to 350F. Lightly dust the surface with flour or additional ground oats. Roll out the dough to approximately 1/4" thick.
Using your desired cookie cutter, cut out the treat shapes and place them on a silicone baking mat or parchment paper lined baking sheet.
Bake treats at 350F for 15 minutes. Turn off the oven, leaving the cookies inside, and let them sit for two hours. This will make the cookies crunchier. For soft cookies, remove them after the 15 minutes to cool at room temperature.
Store soft treats in an airtight container, kept in the refrigerator, for up to 2 weeks. Hard treats can be kept at room temperature up to 3 weeks.
Notes
The number of treats will vary with the thickness of the dough and size of the cookie cutter. This makes 26 treats that are 2" circles.Ground flax seeds are completely optional but a great healthy ingredient to add as they provide fiber and are anti-inflammatory. Talk to your vet for more information. Chia seeds are another great addition.Any type of oats that you have should work well.Talk to your vet about cooking for your dog and any dietary concerns.