I know the conventional method is to remove the upper firewall, then undo sensors and loosen clamps to remove the plenum, then undo and remove the air filter boxes, swap out the filters, and go back the way you came. I think I saw a video showing that it was possible to just undo the air boxes from the sides and slide the old filters out and new ones in. Will that work?

If your hand structure is small ( few muscles and small profile), you can squeeze in your hands inside. This is how I did it but not recommended. I gained some cuts on my backhand because I jammed my hand inside tight space between the air filter. Four bolts on each box by the way. If you have 1/4” ratchet and some small torx bit, you might be able to pull it off. I will take a pic when Ihave time of the tools I used to get into that small gap.

The time saving by doing the above is 10minutes as compared to original method of removing the box. Not worth the trouble. But the answer to your question is YES, it is possible.