When I shoot a left handed bow, I just close my right (dominant) eye. By the time I decide to take a shot, I've already used my binocular vision to estimate the distance. All that's left is to direct the arrow to the target, and only the dominant eye does that.

Closing the dominant eye automatically makes the open eye the dominant one. I know it's against all "The Rules" of shooting, that you must keep both eyes open while aiming and all that... but I don't care. All that matters to me is hitting what I'm aiming at.

Anyway, that's my simple solution.