I saw a cute ornament idea so tried it. First cut a section off a toilet paper roll.
Then cut yarn strips. How many and how long will depend on the size you cut your toilet paper roll I had to experiment for a few minutes.
Loop your yarn around the cardboard.
Pull yarn through the loop and snug or up.
Continue this process by tightening the loop and sliding it against the next one until you have the ring full.
Once you have it all. All the loops into the middle and pull out and straighten up. Tie it off and then trim the top to make a pom pom.