Step 1: Place a dot of glue in the middle of a Styrofoam ball. Place the end of yarn in the middle of glue dot to secure and wrap the yarn around the Styrofoam ball several times through glue dot.
The beauty about working with yarn and Styrofoam is that the yarn "clings" to the Styrofoam texture, making it easy to wrap the yarn around the ball and not worry about the yarn slipping from place.
Step 2: Wrap yarn around Styrofoam ball several times in the same direction, then switch directions. Keep wrapping yarn around ball in alternating directions to get a "yarn ball" effect, as seen above.
Keep wrapping yarn around until Styrofoam no longer shows through. Doesn't that look pretty?
Step 3: When the ball is wrapped to your liking, place a dot of glue next to the most recently wrapped area of yarn. Continue to wrap yarn over glue dot to secure yarn in place.
The yarn ball should look like this afterwards, the glue is covered by yarn wrapped over it. Cut yarn, leaving a long tail for weaving in the end.
Step 4: Thread a needle with the yarn end and pass needle underneath several sections of wrapped yarn. Repeat a few times to secure, then trim yarn end close to ball.
Step 5: To make a hanger for the ornament, use a needle and thread a length of yarn underneath a section of wrapped yarn. Tie ends into a knot at desired length and hide knot underneath wrapped yarn section.
Repeat for lots of yarn ball goodness to hang on your tree this year! So much cuter than store-bought ornaments.
Via: Sew Wrong