Cut a pipe cleaner in thirds. Twist two pieces together then add the third to make a snowflake shape. Trim ends to make sure it fits in the jar without touching the sides.
Tie a string around the snowflake and then to a straw or pencil making sure its short enough that it doesn't touch the bottom of the mason jar.
Pour the boiling water into the pint jar. Add the 6 tbsp of borax and stir until combined.
Lower the pipe cleaner snowflake into the jar and let sit for 24 hours.
Pull it out (it might be stuck to the side) just wiggle it gently. Wipe off the liquid and enjoy!
Notes
Note: Borax is toxic to dogs and humans if ingested. Would recommend doing this with older children or supervised!