Start olive thread on the Ahrex FW562 and tie in a single strand of Crystal Flash sticking out the back, then a small bunch of olive mallard flank over it. The flash and flank together read as the trailing shuck of a drake that never got out of its nymphal skin, which is the whole reason a cripple works when duns are being refused.
Tie in a second strand of Crystal Flash at the rear as your rib, then dub the body forward to about the 70% mark.
Counter the flash forward over the dubbing in open spirals to create segmentation, tie it off and trim the excess. One strand is plenty; the point is a hint of shine in the body, not a flash fly.
Stack a clump of deer hair and tie it in at the front, doing your best to keep it sitting on top of the shank rather than spinning around it, then trim the butts out.
Tie in a hackle feather and take four or five turns at the front, tie it off, then sneak the thread down in front of the wing to prop the deer hair up at an angle.
Whip finish, turn the fly over and trim the hackle flat underneath so the body rides down in the film. Sitting low is what separates a cripple from a standard dry.