Preheat the oven to 350°F (175°C) and line two sheet pans with parchment paper to prevent sticking and ensure even baking.

In a large bowl, whisk together the oat flour, white rice flour, almond flour, tapioca starch, baking powder, and salt until fully mixed without lumps, creating a uniform flour blend for the dough.

Incorporate the maple syrup, raw cashew butter, and vanilla extract into the dry mixture. Stir until the mixture comes together in a rough ball, initially shaggy in texture. Press with the back of a spoon to help the dough start forming.

Using your hands, knead and press the dough several times until it forms a smooth, cohesive ball without visible flour. The dough should be non-sticky and easy to handle. If sticky, wrap in plastic and chill for 1 hour.

For easier rolling, wrap the dough ball in plastic wrap and chill for 30 minutes. This step can be skipped if dough is manageable at room temperature.

Place the dough between two sheets of parchment paper. Roll evenly from the center outward until the dough is ¼ inch thick, ensuring consistent baking and texture. Avoid rolling thinner to prevent overly crispy cookies.

Use cookie cutters of similar size and shape to cut cookies closely on the rolled dough. Carefully peel away excess dough, lift shapes, and transfer to parchment-lined pans. Reroll leftover dough to use it all, yielding about 20-24 cookies.

Bake one pan at a time for 7 minutes (6 minutes if omitting almond flour). Cookies are done when bottoms are lightly golden and edges just start browning. Watch closely to avoid drying out or overbaking.

Let cookies cool on the pan for 5 minutes, then transfer to wire racks to cool completely before icing, ensuring the icing adheres properly.

Whisk powdered sugar, coconut or soy milk, maple syrup, and vanilla until smooth and toothpaste-like in consistency. Adjust sugar or milk to achieve proper thickness for outlining and flooding.

Outline cookies with icing to harden quickly. If flooding or coloring, thin icing slightly with milk and add color as desired. Allow iced cookies to dry several hours, preferably overnight, on wire racks uncovered.

Store uniced cookies covered with foil or in a glass container to maintain crispness. Avoid plastic to prevent softening.