Break off a dime-sized piece of brown clay, a dime-sized piece of white clay and a quarter-sized piece of black clay. If you do not own clay in these colors, use similar colors like charcoal or raw umber.
Work the clay between your fingers to mix the colors together. If you cannot reach your desired color, add more clay of the right color.
Roll the clay into a ball. Gently mash the clay down so that the ball spreads out. Do not flatten the ball completely. Ideally, the flattened clay should be 1/4 inch thick.
Push two sides of the pancake clay together with your fingers to form a point. Press your thumbs into the bottom of the clay, opposite the point, to create the base of your arrowhead.
Pinch the outside edges of clay together the entire way around the perimeter of the triangle. Carefully create small valleys and rough edges on the surface of your arrowhead with the flat part of the butter knife. This will give your arrowhead shape and texture and make it look more realistic.
Place your arrowhead on an oven-safe glass container and put it into the oven.
Look at the original packing that came with your clay for baking instructions. Polymer clays should cook at a temperature no hotter than 300 degrees, but this will vary based on the brand of clay. In general, the clay should cook for 15 minutes at 275 degrees.
Remove the glass container from the oven after cooking.