Hand Tools Archive
The back posts are first squared as they come off the log, then into octagons. The flat part above the seat is also done at this time, before the back post is steamed and bent on a form. Hope you can see this in pic.
After it dries and is off the form the slat mortises are chopped and the post rounded.
The rectangular blocks that you see at each end of the front rung are actually part of the front rung. They provide a home for the front leg tenon and the side rung tenon. The seat material, once in place, is even with the top of the rectangles; when sitting, you do not notice it at all. Hope you can see this in this pic. On the left is the same chair with the seat warp in place and the side rung still uncovered. On the right is a similar chair (in walnut) with a finished seat.