RJG2
Masterpiece
You could also try a wire tourniquet if the base isn't too uneven.I need to do the exact same thing to my Eastern Larch that you did. Im afraid though. Not sure I want to do a girdle, but perhaps just make some vertical slits around the trunk . The top is wonderful as I been working on it for quite a number of years.
If it is uneven you could try concrete. Like this, only without stripping the ring: