How to finish the foot on an uneven natural edge bowl?

[Dawson Mossman]

Guys, I'm working on a natural edge burl that is quite uneven. I typically use a donut chuck to mount my bowls at the end and finish the footing, but due to the very irregular rim that's not working out too well this time. I suspect I'm going to come across this problem more and more as I continue with natural edge projects. What solutions are there for dealing with this situation? I basically need something that can hold the bowl securely in the headstock while completely exposing the bottom so I can clean up a recess or spigot.

Thanks again!