Basically turning the main body into a cylinder Derek, then boring the centre out with a forstner bit for starters.
Then working from each end opening up the bore as required with a 1/8" square HSS bit, further enlarging of the central bore as far as I dare with a 10 X 8 mm HSS tool (narrow flat stiff scraper style) from each end before attempting to thin the walls further with external shaping.
A few more glued up blanks to clear then it's a move to smaller versions as I've had requests for some suitable for miniature trees, guess I'll need to make some smaller tooling for those but they will be of the same simple form using square section HSS blanks that enable no nonsense material removal.