Tape one end of yarn to the cardboard as shown. Wrap yarn around the cardboard. The more you wrap, the fuller your pom-pom will be.
Cut a small piece of yarn. Put it under your wrapped yarn through the small rectangular window and knot it securely.
Gently slide wrapped yarn off your cardboard. Trim the ends of the loops with fabric scissors, making them uniform. Leave the middle tie long so you can knot pom-pom to the headband later.
Make several pom-poms in the same way.
With the long strings, tie the pom-poms onto the headband. Trim the excess to match the length of pom-poms. When done, trim all your pom-poms to a size that suits your wearer. Enjoy!