You will need:
A piece of fleece. (about 1' X 2')
A tape measure.
A sewing machine, or needle and thread.
You can use leftover fleece from another project, or cut up an old sweatshirt or blanket, or buy a cute piece in the remnants section.
Step 1: Measure the head.
Then measure about how tall the hat should be, from the eyebrows, to the top of the head.
For my hat I have a head circumference of about 22" and a height of about 7"