Thread by @Trematomus

We are clearly in this for the long run. Air filters will be there for a while. Why not try to integrate them in the furniture ? Inspi @ee_kelsey
A Starkvind is a perfect fit below a Raskog trolley for a single filter box with a plenum. You could even use the pretty bamboo top.

Starkvind fit tightly in the large side of the cheap triangular Vesken shelves (<10€). Block the other sides with fans in cardboard using tape: you have a filter shelf.
With a bit of coaxing, you can convince a Starvind to fit in a narrow Billy. #ikeahacks #CorsiRosenthalBox

Then a carboard shelf on top with fans (or holes in a real shelf you will not use), a real shelf below and there is minimal tape use.
Basically any shelf of the right size could serve as a box structure (with appropriate distance from walls for air circulation).

Add colorful leds (à la @CRBoxKits ) and you have a cool structure that is easy to fit in the room (because it is already in it) and barely visible with the right color of tape.
(Have I gone through the house trying to fit filters in everything? You have no proof)

I have not tried the fit because I only bought Starkvind filters and not the smaller Fornuftig, but from the dimensions it should be possible to make a 2 filter box (with a Fornuftig as bottom, Starkwind as front, and fan shelf on top) in a Billy shelf.

Enhet 40x15x75 shelf works too for a less massive construct, with the fans on the side. 140mm fans push the filter out partially, 120mm are good but only two fit on top of each other, might not be powerful enough. Possible to put fans on both sides but might be counterproductive.