I would suggest laying down on the ground assuming there is a spot without thorns.
I have never practiced shooting prone and yet I've shot two animals from that position with no range pad, bipod, etc. Most of the time an animal isn't going to wait around for you to get your range pad, etc. One was a deer I took with one shot from 360 yards with a 22-250. The other was a Wyoming antelope I took from probably 280 yards with a 300 Weatherby Magnum.
One note of caution. I once attempted a prone shot on a groundhog with a Thompson/Center Encore chambered in 25/06 that gave me the worst scope bite of my life and required stitches. The groundhog lived to see another day. The stock design of the Thompson/Center Encore does not lend itself well t prone shooting.
On second thought, though I never specifically practiced for the event, I did shoot some CMP matches with a Garand or an M1A in which some targets were shot from the prone position.
