Also everything is clear. But don't confuse the sides of the magnets. I'm not very careful, so there was glue everywhere.
It works:
Cutting the sponge
We cut pieces from a new regular kitchen sponge and simply insert them tightly. No glue is needed.
Using it
Well, that's it. Does it work? Yes. After printing dirty leftovers (~400 grams), the sponge looks like this:
Will I always use this filter? No. There is a risk that the sponge will be pulled into the extruder (I've seen such cases online).
So I plan to use it only under supervision and only in cases where I know the filament is really dirty.