you could place ur camera where you want it then if possible use a pump (shutter) release, hold the subject in your hands and as soon as your ready put it down and once you've whipped ur hands away (asap) and using your foot press the release. an easier way is to get some one else to place it down where you want it as soon as u are ready and u take the picture once their hands are out of the frame. Although i think Michelle A's idea could be easier to pull off in the long run.