Stash..
BUT if you plan on using it for just that purpose Id find a bag/box/tote to put all the 'ingredients' in so you dont mistakenly use it for something else.. Been there, Done that !
IMHO a UFO is a project started and not quite finished.. Sometimes one gets bored and another pattern crosses our paths and we just cant wait to begin the new one and it gets tucked away and put aside.. And thats how it begins.. slowly...first its one, then two.. then when its waaaaay to late you realize you have a doz or so UFO's patiently waiting to be the top LOVE again.. lol..
Today IM making one of my UFO my top LOVE... ONE down only 18 more UFO's to go !!!