Can't post a pict but I will give you my best description.
Get a 2X8 or 2x6 x 8 ft , Small piece of 2x4 approx 12 inch, 2-5/8 threaded rods 4 foot long. Also 4 washer , 4 nuts. And all the large cardboard boxes you can find. I get mine from a bike shop and raid the hardware store dumpster.
Cut the 4x8 in half. now you have a top and bottom frame. Cut the 2x4 in half and nail to the edges of the 2x8, These will raise the bottom 2x8 off the ground by 4 inches. It is the bottom of the frame. Drill holes about 5 inches in from each side of the 2x8. Note it is best to lay on 2x8 over the other and drill two holes directly throgh the top and bottom frame so the holes allign.
Start cutting cardboard into 14" x 42" strips and keep stacking it on the bottom frame until it reaches 36 - 38 inches high. You need a fair amount of cardboard. Run the theaded rod through the bottom frame so it is sticking up. Keep stacking the cardboard. Lay the top of the frame over the cardboad and run the threaded rod through the holes in the upper frame. Put on the bolts and then keep tightening to compress the cardboard as tight as possible. I find I need to rotate sections of cardboard from the outer edges every so often and re-compress the cardboard. I have had this set up for two years in the back of my garage. Arrow tend to penatrate about 50% through. Sometimes you get a soft spot if you shot into the same area all the time some mix it up a bit.
Works pretty well, weighs a ton, I think I spent $25. for wood and rod, cardboard was all free.