The easiest pattern I have ever seen for the green drake is to simply tie in 3 hackle tips for a tail, one brown and two grizzly. Palmer the three feathers to right behind the eye. Tie off, whip finish and that's it. Tied on a 10 or 8 2x long. Although, I have never used them during the drake hatch as someone taught me this fly a couple years ago and I haven't been able to make it home since learning it, it is extremely easy to tie and while not as pretty as some other patterns looks "buggy" enough to catch fish.