Its a fiddly job but can be done.
Assuming sidecovers are off and the front backing plate is in place and bolted in.....I push the surround through and then over the front backing plate so that it sits up forward over the plate until the surround hits the carbies.
I then slide the air filter element in place, it is usually happy to sit over the rubber grommets and the inlets.
I always have the clamp bolt for the clasp/clamp screwed out as far as I can, ready and within easy reach.
I then slide the back backing plate in and then while pressing the two backing plates together and sandwiching the air filter element I bring the surround back and into position over the two plates. I keep pressing the plates together and get the outer lip of the surround over them.
Then while holding all this together, I grab the clamp and push it into the holes I want to use and begin tightening it up.
As I incrementally tighten I push on the two backing plates and make sure they are inside the outer lip of the backing plate, sometimes you have to back the clamp off a turn to help 'pop' the plates under this lip. Continue tightening the clamp and pressing the 'sandwich' together. Done!!!
I find that laying chest down on the bike seat in line with the bike is best for the last bit.
Then sit back and admire the marvels of modern engineering
Also be thankful its all metal, I had a '98 Thunderbird Sport and it had a plastic airbox that basically cracked, fractured, and fell apart inside 40,000km.