This is an easy to make adjustable peg board style chair. It uses one 3/4 inch (18mm) and one 1/2 inch (12mm) pieces of birch or other hardwood plywood. The 3/4 inch (front) board is about two inches longer than the back (1/2inch) board to allow the chair to lean back.
I used a plunge router and a simple jig to cut the rectangular peg sockets but a portable jig or saber saw will also work.