One of the nicest ideas about self assembly is that you chuck all your ingredients into a bucket, give it a stir, and go make a cup of tea while the wonders of the nanoscale assemble a packet of chocolate digestives, a fruit cake or whatever you programmed your ingredients to make. Theres need to make anything one atom at a time, or worry about molecular precision if you can get all your ingredients to assemble by themselves.
A paper in Nano Letters gives a clue to how this might be accomplished, theoretically at least.