northman-
Given that a geodesic sphere has a circular-shaped base, how do you intend to handle the transition from the square shape of the post to the sphere? I think you are looking at an incredible amount of work, especially if you are wanting the sphere to be an integral part of the post. If it were me, I'd create the shape from a separate piece of wood and attach it to the top of the post when I was done. Even then, I doubt you can cut this easily with power tools, like a table saw. The best suggestion I can make is to get a turned wooden sphere the diameter you want, lay out the pattern on the sphere, and shave the faces flat with a sharp chisel.

Here is a link that might be useful: Paper model