Takes 5 min, little patience and a band-aid(s)!
Materials:
1 high-end
used(reinforced pleat) central HVAC filter - practically free!
Tools:
Utility Scissors or Wire Cutters
Pliers/Vise Grips
Drill or lots of patience - I recommend the drill!
Look at the picture next to last - that thing is sharp so be careful coiling it or ... you remember that band-aid from the top, right?
)
Have fun!