For about 2 weeks with your hips and knees slightly flexed (pillow under knees). Then in theory, you can lie on your side for the next 2 weeks. You may see more swelling on the side you are resting on. By 6 weeks, you should be relatively comfortable but i would advise not lying on your front for 3 months.
Although the timing to sleep on your back after tummy tuck varies greatly from surgeon to surgeon, it is important to prevent tension on the incision for a reasonable amount of time to ensure proper healing. That "reasonable amount of time" should be discussed with your plastic surgeon. Sometimes you I'll be allowed to sleep on your side early during the recovery process. Touch base with your plastic surgeon for finals recommendations.
