GNU Emacs Lisp Reference Manual
To create a new frame, call the function make-frame.
The argument is an alist specifying frame parameters. Any parameters not mentioned in alist default according to the value of the variable default-frame-alist; parameters not specified even there default from the standard X defaults file and X resources.
The set of possible parameters depends in principle on what kind of window system Emacs uses to display its frames. See X Frame Parameters, for documentation of individual parameters you can specify.
make-frame before it actually creates the frame.make-frame after it creates the frame.