I started by laminating 2 pieces of 3/4" CDX plywood together with glue and screws. Then I painted the whole thing with a couple coats outdoor brownish paint. I then glued up some blocks of 2 x 6 approx. 6"x 6" and glued them up about 9" long to look like a 6" x 6" log x 9" long so I can cut them out at a 10 degree angle on the miter saw. I screwed those to the bottom of the bench and then attached 1 1/2" floor flanges to the 10 degree blocks.
Here's what it looks like on the bottom of the whole thing. The front 2 10 degree angle blocks were also skewed out at a 10 angle towards the front of the bench and the target.
Here it is upside down on my workbench, upside down with legs attached. They are 1 1/2" black iron pipe with the pipe threads screwed into the floor flanges. I had a local guy in a steel shop cut the legs to 36" and thread the pipe with a pipe die. He charged me $50 for the whole shebang out the door.
Here it is right side up now. I coated the top with some non slip grip paint so I can put my Caldwell steady rest up there and not have it slip around a lot. The jury is still out on the non slip paint. Caldwell Steady rest from Walmart $69 and worth every penny I paid for it. Caldwell makes nicer rests but this one has been a dandy for at least 4 years of abuse.