I built a shooting stand / bench maybe fifteen years ago ... I started with three old square grain bins that I cut up and found enough good wood to build a eight by ten shed, cedar siding and roof also, and fir full size two by sixes on twelve inch spacing..
I built the bench part on one long wall, with two inch two by sixes for laid flat for the bench, and four by fours for the uprights, nothing fancy. I then cut out the wall with for two shooting windows that swung up and became sun shades. The shed is still in use for tool storage now, moved into the yard rather than two hundred yards from a sandy berm ..