Buy old portable toilet, $10 in our area. Take out tank and remove base. Clean thoroughly!! Paint to blend in with your stand location.
Build a 4x4 platform using all pressure treated wood. First, build a frame using 4 2x6. Remember, two sides will be 4 ft, two will be 1 1/2 inches shorter. Place measured 3/4 plywood on top, attach using deck screws. Get two 8x4x4s', cut in two. Place one leg in each corner of platform frame. Attach with lag screws through frame and plywood floor. If you go higher than 4 feet, you may need braces and/or tie downs depending on high you go. Place porta john on plywood floor and center. Measure inside outline of portajohn. Cut 4 2x2's to measured lenghts. Place on floor to fit inside outline of portajohn. Deck screws through 2x2's into floor. Deck screws with fender washers through outside of porta john into 2x2s. Cut shooting windows, install choice of seat.
I built mine on sight using battery powered tools.