sgtar15,
You might also consider joining a local rifle club. Look for someone or a club that shoots CMP (Civilian Marksmanship Program, formally known as DMC) matches. These guys know what you are seeking (sling use and positions [;)]).
Traditional prone position is achieved by laying your body at an angle to the target.
If you shoot right handed swing your body left. To find what angle, lay facing the target, holding the rifle at the target, and swing the rifle to your left. It just got more comfortable to hold, didn't it? Now duplicate that angle with your rifle pointing at your target.
There are variations and somebody will probably say I'm not telling you the 'proper' way, but this will achieve what your looking for.
Again, consider, at least watching, joining a club match. You'll learn lots and have fun.