Let your leftover waffles cool completely and then lay them on a baking sheet in a single layer. Place the baking sheet in the freezer and allow to freeze for at least 2 hours. After they become nice and frozen, you can place them in a zip-top freezer bag for long term storage. You can re-heat by placing the waffles on a baking sheet lined with parchment paper and baking at 350-degrees F for 13-15 minutes, or you can pop them in the toaster.