A platform doesn't hold something, it supports it. Here is the basic premise with rifle shooting. If the platform is unstable what it is supporting won't be secure. A wobbly platform means a wobbly rifle equals a wobbly shoot.
I never gave much thought to how I was supporting my air rifle as a kid. My dad had shown me where my two hands were supposed to go, that the butt went in my shoulder and my cheek against the cheek piece. Having sussed that the next thing was to make sure you were able to look directly through the sights that confirmed the barrel was pointing where you were looking.
Firing a rifle of any kind freehand, without any form of aid or support, is a wobbly affair. Target rifle shooting isn't a static sport. The rifle is moving around a lot, much more than you give it credit for as an observer. Dad taught me to squeeze my wrists into the stock and that helped but really it's no good for competitive shooting because it requires muscular effort, or corrective tension. If you're holding the rifle your muscles tire and you wobble more.
The first shooting aid I used was a two point sling of the very basic variety. A two point sling attaches to a rifle in two places. Slings were first developed to carry a firearm over your shoulder and were attached under the barrel and near the butt. It was worked out that you could insert your arm through the sling and hook it around tricep of the arm that supported the firearm. By wrapping the sling around your wrist and holding any excess length between your supporting hand and stock you could impart three points of tension onto the firearm now in your shoulder. It makes quite a difference and the concept was developed into the one point sling for true target rifle.
We have four points of contact with a rifle; supporting hand, trigger hand, shoulder and cheek. With each and every shot they must be in the same place. These points of contact are attached to our body and by extension the body needs to be in exactly the same position for each and every shot. It sounds easy until you gradually realise just how much you unconsciously move around and how much disturbance reloading can cause to your position.
There should be nothing complicated about a shooting position. It needs to be comfortable and simple, especially when you start out. When lying on your front make sure your spine is straight and your hips and shoulders square to your spine. You want a straight line from your supporting wrist to the ankle of the supporting side of the body. We draw the other leg out slightly to give you some stability width ways. The arm of the trigger hand should be such that it doesn't cause an excessive tilt to your shoulders and that they are pretty much parallel to the floor.
Now, everyone is a different shape and size and few positions are the same but these basic rules are the best place to start. Keep it simple and comfortable, put the rifle to your position not the other way around. Building the position should be an ordered process that is consistently repeatable. Imagining yourself going through that process is a great way of identifying errors as you are making them in reality so you can correct them before you begin your shoot.
The platform is the important bit. The platform creates the natural alignment for the rifle. Natural because there's no effort involved and aligned through your body's four points of contact. Being aware of what your body is doing is a really important skill and is honed through mindfulness and yoga. Peace man!