Start the 30D purple nano silk at the 60% mark of the big gap hook. A fine thread is not optional at this size, a normal 70D will double the diameter of everything you tie.
Tie in a strand of purple micro flexi-floss pointing rearward and wrap the thread out along it for a few turns, then wrap back, so the floss forms a slim extended abdomen projecting past the bend about a shank length. Building the body off the back of the hook keeps a big silhouette on a tiny gape, which is why fish eat it and you still hook them.
Trim the abdomen so it tapers to a fine point and put a touch of Bone Dry along the wraps where it leaves the shank, since that joint is the weak spot on any extended body.
Post a short clump of purple ultra dry yarn upright at the 65% mark and take a few horizontal wraps around the base to stand it up. Purple shows up dark against glare, which is why it works better than white on flat evening water.
Tie in the dry fly hackle at the base of the post and take four or five turns parachute-style around it, then tie the tip off under the post and trim.
Whip finish under the hackle at the eye and check the fly sits flat on the water, riding on the hackle and the extended body rather than on the hook bend.