not really what your asking about but what I use the most either on the ground or across the hood of my truck or even over the bench at the range
https://www.midwayusa.com/product/939101910?pid=276544we do have benches at the range and I do used them some , I am not a huge fan of the position a lot of benches put you in very up right and not leaning into the recoil not like your likely to be in the feild.
I also like to be sighted in with a sling , because I know it is what I will have with me later
prone is my preferred position and I have been thinking about building one of the prone benches for the range which is really just a platform to give you a little angle and make it more comfortable to lay there a while and get up and down.
very few examples of them online this is what I would model it after