After many tries, I competed a Cambridge Hybird FP using Bluestone (special pen for a friend using stone from his property in the NY Catskills).
I cut the 1" square blanks using a wet saw, then tried to drill them out. The blank kept breaking when trying to drill the hole for the tubes. The trick was to drill the hole in a large slab first, then cut the blanks. Drilled slow with plenty of water.
Epoxy for the tubes, wet saw to take the corners off the blank, turned slow, taking VERY light cuts with carbide tool. Once it was close, wet sand with automotive sandpaper up thru 1500 grit. I finished with CA, MM thru 12000.
When assembling, I ground the mating surfaces of the components going into the tubes so they were "finger tight", and used a drop of epoxy to secure them. After all that work, i did not want to take a chance cracking the stone barrels.
I was pleased with the end result, but it was a LOT of messy work
joec