How to sleep after receiving a tummy tuck and BBL?

This recovery is difficult.  You have a couple of options.  You can sleep on your sides or place pillows underneath your thighs and lower back.  Ask your plastic surgeon what he or she recommends.  Find a plastic surgeon with ELITE credentials who performs hundreds of Brazilian buttlifts and tummy tucks each year. Then look at the plastic surgeon's website of before and after photo galleries to get a sense of who can deliver the results.Kenneth Hughes, MD, Board Certified Plastic SurgeonLos Angeles, CA

After a Brazilian butt lift, it is ideal not to put too much pressure on your buttocks. In that respect, sleeping in a prone position is optimal. A tummy tuck, however, can leave you with a pretty tight feeling abdomen, making this not possible. 
I would recommend sleeping on your sides with some flexion at your hips. Make sure your bedding is quite soft, and I would rotate back and forth between laying on your right and left sides. 
The worst position immediately following fat transfer to the buttocks is sitting. If you have to sit, do it for limited amounts of time with adequate padding. As far as positions in general, this would be the order of my preference:
Standing or Laying on Stomach > Laying on Sides > Laying on Buttocks > Sitting on Buttocks