Exactly what and where is PRONE LIE? For such a simple position it is often done incorrectly.
Lie on your front with your heels touching and toes pointed. Your face should be parallel to the floor with your nose JUST off the floor. The head should never be lifted as this pinches the back of the neck.
To get your arms in just the right place, take the “Heave” position with your arms then undo your hands and place them on the floor. This will allow your shoulders to relax and all of your chest and arms to be comfortably on the floor, and not be ‘bunched up’.