Set a size 16 dry fly hook and start the gray thread. The 3mm foam cylinder post suits a 12, 14 or 16; on an 18 it is too bulky and you want a different post.
Set the foam cylinder upright about a third of the way back from the eye. Put a couple of tight wraps in behind it, then a few wraps up front to prop it to 90 degrees.
Take the thread back and catch in about a dozen grizzly hackle fibers for the tail — no need to snip the butts square, the dubbed body covers them. Add a few extra wraps to bind the foam butt down harder.
Wax the thread and dub a gray rabbit body (muskrat is the original) from the bend forward to right behind the wing post.
Take one grizzly and one brown rooster hackle and tie both in at the post with a couple of wraps around the feathers and the post together. Make the grizzly slightly longer than the brown so the brown does not overpower it. Run the thread up front and snip the stems off.
Wax the thread again and dub a small thorax around the base of the post and up towards the eye, propping the post back upright as you build it — the wraps tend to lean it forward.
Wind both hackles parachute-style around the post, two or three turns depending on the quality of the hackle. Catch them off by lifting the fibers and slipping the thread underneath, zigzagging the wraps if you need to.
Snip the hackle tips off, then trim the foam post to length now — the long post gets in the way of the finish.
Whip finish underneath the hackle fibers but above the body, keeping the thread clear of the eye, and try not to trap any fibers on the underside.