Items required to make an elf hat are green and red felt, a piece of yarn equivalent to the desired height of the hat, jingle bells and matching thread. In addition, necessary tools include a needle, scissors and a sewing machine.
Using the scissors, cut the green felt in the shape of about 1/4 to 1/3 of a circle, and use the yarn to measure the height of the hat. To determine the width of the base, measure the circumference of your head; the circumference equals the distance along the curved edge of the circle.
Position a rectangular strip of red felt along the base of the green felt until the edge is completely lined, and sew along the curved line, taking into consideration a seam allowance. Cut any excess red felt from below the curved edge of the green felt, and stitch along the curve. Make triangular shapes of various sizes in the red felt using scissors, and fold the hat in half with the red felt facing inward until the ends meet.
Sew at the seam along the height of the hat with your sewing machine, and flip the hat inside-out so the red felt now shows on the exterior. Using a needle and thread, sew the jingle bells to the point of the hat. Inspect the hat for any loose threads or overlapping felt, and make any necessary adjustments.