At first I thought you meant a call for a wood duck, and I thought "gee, never seen anybody turn a wood duck call before!" I should have known better.
I've done a few of these (good fun) but have had real hit or miss luck with the echo inserts. I'd love to make my own inserts, but even a production toneboard jig is quite expensive for the hobby turner.
Also, may I suggest a band to keep the call from splitting? I order from this guy
Home nice rings at pretty decent prices, and he'll do custom work if you order more than a few.