There are two ways (that I know of) to open an unnamed buffer.
The first is before vim has even been launched. You can simply execute vim
from the command-line without any arguments. Follow that by invoking :ls
to see that the current and only buffer has no name.
The second method is with a vim session that is already open. If you invoke
:new, a new buffer will be created that, like the first method, has no
name.