Best way to cover up this hole drilled when installing a ceiling fan?
This isn't common on an open wall, more for shadow boxes and such. However, you could remove that piece of molding and cut another piece with a 45° angle where it meets the corner. Then cut a small piece about 1ft. long with 45° angles on both ends. Then cut yourself a dead end on the left side. You will probably have to cope the excess wood at the corners for the wire to fit better. You can pinch nail both pieces at the top and bottom for a tight fit in that area.

Crown Molding Return