Best I can do:
Fold the sheet in half the same you would the top sheet, then tuck the corner elastic into the other corner elastic, matching it up. Hold onto it and fold the sheet in half again. And again, until small enough. The trick is holding onto the elastic corners.
You are #2 to suggest and I tried it and it Worked.
Instead of final fold I rolled it up as a tootsie roll so I can make the discretion among like TWIN flats.
I did it...and yes it is as another poster put it or so.
Get the corners in your mitts then line up...
I got it done and still found a tuff so once I met my cuffed double corners I folded once and then went in for the (identify the stupid fitted sheet mode) put it away nicely.
Rolled that wild pup up and stacked it next to the flat.
SOB has not moved.
LOL Kudo’s to the posters who taught me how to overcome non compliant sheets and God’s bless wishes that there load are a bit lighter.