Woah woah woah, hold up. Building LEGO "sets"? Ahahaha, haven't done that in a loooooong time! However, I tend to build mocs much in the same way, with all the pieces spread out on my table (ideally, typically it's the floor) and then hunting down the parts I need in an ever-expanding pile of pulled parts. A bit of a mixture of both is probably the healthiest thing. Balance, or somethin', right? ;)