Although it may seem to adults that without a pillow it is impossible to sleep, we have already seen that, given the physical characteristics of the baby up to two years of age, not only does he not need it but its use can be harmful to his back or, even worse, be a cause of sudden death by suffocation.
Regarding the recommended postures at bedtime, we know that it is advisable to place him on his back and never put him to sleep on his stomach. Comfort regarding posture in bed responds to a habit, so if we habituate our baby to sleep on his back from the first day, he will not need a pillow to be comfortable in this position.
To prevent your still soft head from deforming because it is always in the same position, it is advisable to change its orientation from one side to the other. In the crib, you can put a toy or something that catches his eye on the side you want him to face, but not inside, or put the baby to bed alternating between the head and feet.