She flipped from her back to tummy at 3-4 months and could flip back onto her back around 4.5 months. I didn’t train her.. it’s a natural process.. but there’s an acceptable age range.. some babies will do so earlier, and some later, so don’t worry:)
LO able to flip when she was about 3 months. Just lots of tummy time to strengthen their neck and back. Initially baby will try to flip from front to back and got stuck, show(help) him/her how to flip.