Isonychia Mayflies are abundant on my home river and the trout have been especially keyed in on them this season, as our normal Gray Drake spinner falls have been practically non-existent. This has easily become my most productive wet fly for late spring/early summer trout. I fish it using a traditional wet fly swing and give it short twitches during the entire swing. I have also found that using a poly leader (super fast sinking) makes it even more effective.
Step 1: Place a Daiichi #1110 size 12 hook in your vise, wind uni-thread 6/0 light yellow thread so it is even with the hook point. Tie in a small clump of peacock or peacock black IceDub.
Step 2: Fold the forward clump back and tie it off.
Step 3: Fold one strand of Fashabou glow in the dark yellow #6952 over the thread and tie down so it is even with the hook point and on top of the hook.
Step 4: Tie in one small brown hackle feather (with barbs no longer than 1/2") by the tip.
Step 5: Dub some peacock or peacock black IceDub onto the thread and wind forward, stopping about 1/16" behind the hook eye.
Step 6: Palmer the hackle feather forward through the body and tie off.
Step 7: Bring the Flashabou strand forward on top of the hook and tie it off behind the hook eye.