When baby started flipping, how to ensure safety when asleep

My baby has yet to start flipping, but would like to know in advanced. When baby started flipping, when they flip while sleeping, like sleeping on tummy, how to ensure baby’s safety? Like they wont suffocate themselves by sleeping face down ? Aside from no toys, extra pillow and tight bedsheet. And when do i need to turn baby to sleeping on his back? For example if his neck strength is still not so strong.