I'm strictly utilitarian, shooting in the field rather than on a formal range. My rest consists of the sheet of 5/8" ply that lives in the bed of my truck, a sawhorse and a folding chair. Just drop the tail gate, slide the ply partway out and rest the end on the saw horse. Put the chair behind it, and I'm ready. Takes about 30 seconds of setup.
When I'm shooting somewhere I can't position the truck right, I just rest the ply on two sawhorses. With two sawhorses, if you keep them about 18" in from the ends of the plywood, the span between is plenty stiff for shooting work.
If the ground is uneven or for some reason the table doesn't seem stable enough, I just set a heavy shooting box or a few rocks on it right over the sawhorse(s).