How to prevent a flat head on baby?

In India, we have a very tried and tested method for preventing flat head on babies. Take 1 Kg of mustard seeds and fill them into a DIY baby pillow and stitch it up. Make the baby’s head rest in the centre of the pillow whenever he lays on his back. It worked with both my kids and now trying it out with my third.

Disclaimer: I know many countries including US have laws regarding prevention of SIDS so please try this at your own risk and under careful supervision.