Just did it myself
Super easy, but I have a little to add to the great write ups mentioned above.
The point of the mod is to still be able to close the box up if needed (off-roading, fording a river) and have a water tight seal.
Well when I was putting the deck plate in I noticed 3 small holes along the bottom of the airbox, which I've tried to identify in the pics below. Looking down into the box, one is on either side below the spring clips for the air filter and the 3rd is right in front below where you'll put the plate. Most likely these wouldn't let a ton of water in the box, but if the entire point of putting silicone around the deck plate is to create a water tight seal, it might be a good idea to dab a little silicone in each of these holes to close them up for good. That's what I did, just thought I'd mention it. Good luck with the mod, it's really easy!