make-flyspell-overlay

make-flyspell-overlay is a compiled Lisp function in `flyspell.el'.

(make-flyspell-overlay BEG END FACE MOUSE-FACE)

Allocate an overlay to highlight an incorrect word.
BEG and END specify the range in the buffer of that word.
FACE and MOUSE-FACE specify the `face' and `mouse-face' properties
for the overlay.