I think it is a kvisah problem; not a hachana problem. Look in a shmiras shabbos k’hilchasa; I’m sure you’ll find the sources.
15-45. He says it’s both (Not really k’visah; nireh kim’saken).
The source is S.A. O.C. 302-3. He says it is muttar to fold clothing on Shabbos l’tzorech Shabbos l’lovshom bo bayom (only for that day).
M.B. clearly implies that the reason is because it looks like m’saken mana (sp?), based on Rashi, bd”h bishnei, yeshonim, and tz’vuin (first three Rashis on the second Mishnah), Shabbos 113a.