We had a metal shop class build some very similar to this one above, but with a slanted roof covered with corrugated metal, and a slanted scoring table in front of the chair. We used Trex decking for surfaces. Here is a picture of ours.
I can sell you templates for this chair for $50.00. You just buy 2x3s at Home Depot and lay the template for each piece on the 2x3. The template tells you where to cut, at what angle and where to drill for assembly bolts and screws. The templates can be used to make as many chairs as you like. You also get a parts list and assembly instructions.