Piece of 3/4" treated plywood, a pair of folding banquet table legs. Put EMT tubing in the legs to make them a bit longer, used crutch tips with washers inside (so the EMT didn't cut them) so the tubing wouldn't pack with dirt. Pretty durn stable and it folds away less than 3" thick.
Sturdy enough to hit rocks at 1,000 yds with a bipod and rear bag.