To make a brim, first measure the diameter of the bottom of the cone; divide this number by two to get the radius. Add a 1/2 inch to the radius and mark that length on the paper compass (point A to point B). On the hat paper, draw a circle using the radius. From the same center point, draw a larger circle 3 inches outside of the smaller circle (point C). Cut out the resulting doughnut shape, cutting straight through the brim to get to the center circle.