The American Academy of Pediatrics recommends that baby should play more on the stomach under the supervision of an adult and parents hold baby upright when the baby is awake. Specifically, we can do this:
Hold the baby upright;
Change left and right hands/shoulders frequently, when holding your baby;
Always put your baby on the bed in a supine (back down) position to let your baby sleep;
After falling asleep, the baby turns over and becomes side-lying or prone, and there is no need to help her/him adjusting the posture;
Help the baby adjust the head orientation, try to avoid the baby’s head sleeping on one side for a long time (but still let them lie on their backs).
Note that when you let your baby play on his stomach, adults must take care of it!