Preheat oven to 350ºF and line a baking sheet with parchment paper. Set aside.
Combine all dry ingredients in a bowl and mix together.
Add water and egg.
Mix ingredients together until thoroughly combined with a spoon. Then, with your hands, knead dough. This dough will feel very wet and sticky. Let it sit on the counter for 15 minutes, allowing the oats to soak up the water and egg.
Sandwich doughball in between two pieces of parchment paper. With a rolling pin, roll dough to about 1/4" thick. Stamp with cookie cutters and place biscuits on the baking sheet.
Use a cookie cutter to stamp out biscuits and place each treat on a lined baking sheet.
Bake at 350ºF for about 30 minutes, or until cooked through.
Transfer to a wire rack to cool.
Store in an airtight container for up to a week on the counter, two weeks in the refrigerator, or three months in the freezer.