Need advice on doing hewn out turkey call

[jcdart]

Hi. This is my first post here. A newbie. I would like some advice on how to cleanly hewn out a turkey call. I use a Forstner drill bit to get the big stuff out but there are drill marks and pilot holes in the bottom. Also the sides and corners need squaring up.

How best should I hewn out a call. Should I use chisels instead of a drill bit or combine them. The look I want is a nice clean hole with even sides and the bottom flat without alot of marks. I do not know how this can be done.
The hewn out hole would generally be 1 and 1/2" deep or maybe 2".
The hole would be usually 1 and 1/4" wide by 4" to 6" long.

I will greatly appreciate whatever advice you have for me.

Thanks,

jcdart