I have used normal indolium pan that i use for making kulipaniyaram,but you can use a non-stick one too.
Using non-stick is much easier but as am used to this pan I was comfortable.
When cooking this appam you can close it with a lid or cook as such.
Adding baking soda is optional.
You can cook all with ghee alone if you wish but as I don't prefer that I have mixed oil and ghee.