Preheat the oven to 350°F and line a cookie sheet with parchment paper or a silicone mat.
In a large bowl, stir together the peanut butter, coconut sugar, milk and vanilla extract.
To the same bowl, add the almond flour, oat flour, baking soda, and salt (if using). Fold everything together until evenly combined and a dough begins to form.
Scooping out about 1½ tablespoons at a time, use your hands to roll each scoop into balls.
In a small bowl, stir together the cane sugar and ground cinnamon. Roll each ball in the cinnamon mixture until evenly coated. Transfer to the baking sheet.
Using a fork, press down on each ball in a criss-cross fashion. The cookies won't spread much on their own so be sure to press them down to roughly ½-inch thick.
Bake in the oven for 10-12 minutes. Allow to cool completely then enjoy! Leftovers can be stored in airtight container for up to 5 days, or frozen for up to 3 months.