Step 1: Get a Box, Razor, and Packing Tape
Step 2: Tape up the box
Step 3: Grab your vent
Next, cut the outline you just made with your razor and pop out the cardboard.
Keep the cardboard that you just cut out, you will need it later.
If you wish put the vent in the hole to test if it fits... Mine does, perfect fit =)
Step 4: Put it over your vent and cut a hole
Next I got my razor and just cut a hole, didn't really madder on what size, but its pretty big on mine. Once again, keep this peice.