What I do is have two solid black (and slightly blurred) overlays to act as eyelids, each with a curve to better represent eyelids, but some people just use straight ones without a curve.
Each eyelid overlay covers half of the screen (top/bottom) to make it initially appear all black and then I shift the top one up and the bottom one down to “open” the eyes and shift the top lid down and the bottom lid up to “close” the eyes. (:
