I have my wife sew them up. Just go to a fabric store and get some Muslin, very cheap stuff Cut to sizeand fold in half then sew along the open side and bottom. I like to make them from pieces 16" long and 7-9" wide.
Wet then ring out cloth casing before stuffing

I use sugar maple because we have lots of it here, use what ever hardwoodyou have locally just not any evergreen