Look at old photos & drawings of men (mostly soldiers) shooting the Krag at long range.  Some used a sitting position with the rifle held crossways in their arms.  The sling is used to help steady the rifle.  From prone, there were a couple of back rest positions.  The sling was wrapped around one leg to absorb recoil.  You have to be a bit of a contortionist.  A shooting mat or pad is probably desirable.