Its difficult to keep up with demand for this style due to the size of the billet of wood required. The seasoning is of course critical as any serious warping will break the glass or trap the mechanism in its socket. Techniques for drying the larger lumps right through took a lot of trial and error development. The old timers reckoned on 1 year to the inch thickness and they didn’t have to contend with modern centrally heated houses.
I start the process with a year or two outside then finish off with two months in a small kiln. I also use an electronic moisture meter to be sure.