I would think, as an amateur dice maker, but with a lot of experience with carving wood and restoring antique furniture, that briar wood, used in making pipes, wood be an excellent wood to use. Most any hardwood, cherry, maple, English walnut, would make excellent dice. Briar pipe kits come with a good sized block of wood that could possibly make four to six dice. You would have the challenge of finding a pleasing pattern to the wood while keeping good balance. A jigsaw or scrollsaw can be set up easily to make the precise and even cuts for each side of a given die. Definitely something to look into, but the cost to churn out a good set of dice might keep all but the most hardcore collectors away. The cuts can be made accurately, but it would be tedious handmaking d20s.