after the tree dies just snap it off and break the mass of pebbles in
two and scrape them off.
I got two nice little pots this way at a garage sale. I snapped the
dead junipers off and threw them in their trash.

A bit of soaking and a scrub down with a teflon pad freed the pot of
its pebble shroud. Rootball went in compost and voila, two shohin
sized pots.