Starting with Flash #293 (January, 1981) where George even drew half the issue (teaming up with Firestorm to face the Atomic Skull), as it was his only Flash cover, and adding the iconic image from Crisis On Infinite Earths #8....well, just because!
Well, that was George's only pre-Crisis Flash cover, as he covered Flash (Wally, instead of Barry) for a few issues early in his run.
Flash #15 and #16
Flash #17 and Annual #2 (inked over Mike Collins' pencils)
Flash was also featured on covers of the Justice League of America and New Teen Titans as well....Logan's Run, Green Lantern, Justice League of America, New Teen Titans, some on his birthday, and more to come, to keep George's legacy alive.