(let ((gf (ensure-generic-function 'move)))
  (make-method-lambda
    gf
    (class-prototype (generic-function-method-class gf))
    '(lambda (p l &optional (visiblyp t) &key color)
       (set-to-origin p)
       (when visiblyp (show-move p 0 color)))
   environment))

During macro-expansion of the defmethod macro shown in this figure, code similar to this would be run to produce the method lambda and additional initargs. In this example, environment is the macroexpansion environment of the defmethod macro form.