Just finished building up a cork grip. Some history for context. I had built a 10 foot rod with cork grip but left the butt as a split. Got sick of looking at the blank and started to wish that I had used cork for all of it. So I embarked on seeing if I can make it all cork without destroying the butt grip. First I made some cork dust granules by planing a piece of cork straight into a bucket. Then I put a thin coat of epoxy adhesive on the blank and sprinkled the cork dust and pressed it into the adhesive and let it dry. Then I used pva glue as the next coat and sprinkled more cork dust. After getting the diameter I want and after the cork set I sanded the cork. That's it. Actually it looks rugged and it's not as fine a finish as using cork rings but a doable little project. Whole thing added only 15gram weight to the rod

Ken,
Another option was to ream cork rings to diameter of blank - then cut the rings in half to make "half moons" - then epoxy the two halves together around the blank.
Wrap with plastic wrap and clamp with hose clamps.
The seam is just about invisable.
Herb