Are you committed to using wood? If so, I would suggest rock maple. You may be able to get 1 inch to 1 1/2 inch thick slabs like the BoosBlock.
If you are not committed to using wood, look into getting some 1 inch thick granite slabs from a local dealer that does kitchen counter work. They may have some scrap laying around that you can have cut to size fairly inexpensively.
It will be easier to get threaded cones mounted to maple than it will for granite, but, there are several folks who post here who do use the slabs of stone as bases for their speakers.
If you are not committed to using wood, look into getting some 1 inch thick granite slabs from a local dealer that does kitchen counter work. They may have some scrap laying around that you can have cut to size fairly inexpensively.
It will be easier to get threaded cones mounted to maple than it will for granite, but, there are several folks who post here who do use the slabs of stone as bases for their speakers.