Fix the eyes first: take a 1 in. length of 20 lb mono, melt a small ball on each end and slide a small black glass bead onto each (or use ready-made bead-chain eyes). Figure-eight this across the top of the shank about two eye-widths back from the eye and lock it down.
Run the olive thread to the bend and tie in a slim clump of olive marabou for the tail, about one hook length long. Long enough to flex and 'swim' but not so long the fly fishes like a tadpole.
Tie in the fine gold wire at the bend for the rib.
Wind the marabou butts (or dub olive fur) forward to just behind the eyes to build a slightly tapered abdomen.
Rib the gold wire forward in 5-6 evenly spaced turns, spiralled opposite to the body so it locks the marabou down, then tie off and break off the excess.
If adding a wing case, tie in 6-8 dyed-olive pheasant tail fibres pointing forward over the eyes now.
Dub a pinch of olive fur and figure-eight it around and between the mono eyes to build the thorax.
Tie in a dyed-olive partridge hackle by the tip behind the eye and take 2 turns for sprawling legs; if you tied in a wing case, pull the pheasant tail fibres over the top of the thorax and tie down behind the eye. Whip-finish. The marabou tail is the whole point. It pulses like the wriggling natural on the retrieve.