You can find free pallets all over the place. Use this old lumber to build a box, preferably at least four feet high. Fill with dirt or gravel. You can use rocks, as well. Use angle braces in all directions, or the dirt will start forcing the corners and sides apart.
I use an old piece of plywood to cover the front, and staple cardboard to it. I then tape or staple the paper targets to the cardboard. Use a carpenter's level to draw a horizontal line across, to serve as an index for the targets.
Always set your paper targets as low to the ground as you can.
You will eventually begin to eat a hole in the center of your aiming-point area. Clean up the splinters, and nail on a new piece of plywood.
FWIW, Art