The wood I used to make the chair frame was treated dressed (smooth/planed) pine and had a finished size (width and depth) of 75mm x 75mm.
That is not a common size wood but it is the size that I wanted, so I more or less had to rip and plane it out of bigger wood.
A more readily available dressed (smooth/planed) wood size is approximately 90mm x 90mm. In retrospect I would have used 90mm x 90mm, as I think that the king's chair could have handled a slightly bulkier look.
Basically, If you use any stock size between 70mm x 70mm and 90mm x 90mm for the chair frame it will look just fine.
In total, allowing for a bit of waste you will need
7.3m of 75mm x 75mm exterior type wood
(if you are unable to get your hands on 75mm x 75mm wood, then any stock size between 70mm x 70mm and 90mm x 90mm will suffice),
3m of 90mm x 45mm exterior type wood,
4.2m of 25mm x 25mm exterior type wood,
4.5m of 150mm x 25mm exterior type wood,
and 2.7m of 12mm diameter dowel (round wood).
You will also need...
56 of 75mm wood screws (exterior type),
32 of 35mm wood screws (exterior type),
130mm galvanized coach bolts with nuts and washers,
exterior type wood glue,
and some type of wrought iron or metal design to fit to the back of the king chair.
Click on a plan picture in the right hand column to see a larger picture of the plan drawings and also the arm detail drawings.
I did not use any fancy joining methods, I simply just glued and screwed. However because of the thickness of the framing wood, I first drilled a 12mm diameter hole more than halfway into the face piece of wood (where each screw went) and continued all the way through with a smaller hole (screw shank thickness).
Why the 12mm diameter hole more than halfway into the wood?
It saved using humungous sized screws, and although it left 12mm diameter holes in the wood where every screw went, it was just a matter of plugging the holes up with a bit of 12mm dowel.
The end result looked great and was in keeping with the type of chair.