Clamp a 60-degree jig hook in the vise and start thread on the shank behind the jig eye.
Slide a tungsten bead onto a sequin pin (or a short length of stiff wire), then lay the pin along the top of the shank so the beaded end projects FORWARD past the jig eye by roughly one bead-plus-a-little; this extension is the balance point that makes the fly hang level.
Lash the pin firmly to the shank with tight thread wraps along its length, add a drop of superglue, and wrap over it again. It must not rotate or slip; trim any excess pin at the rear.
At the rear of the shank (above the barb) tie in a full marabou tail about one and a half shank-lengths long; bind the butts forward to smooth the body.
Tie in Ice Dub or a dubbing brush and build a baitfish-tapered body forward over the shank to just behind the bead, fatter in the middle and tapering at both ends.
Brush out the body with a dubbing brush or Velcro to blur it into a translucent minnow shape, then sweep the fibers back.
Whip finish behind the bead. Optionally glue a 3D eye to each side of the front of the body and coat with UV resin or head cement to lock everything.
Check the balance: hooked through the pin loop under an indicator, the fly should hang dead horizontal.