Optional: wrap 8-12 turns of lead-free wire over the middle of the shank for weight and cover with thread, leaving thread at the bend.
Tie in a sparse marabou tail about one shank length long, half the amount you think, so it slims and pulses rather than clumps.
Tie in the mohair yarn at the bend (and a copper rib if you want durability).
Wrap the mohair forward in touching turns to just behind the eye, forming a shaggy body, and tie off. If using a rib, counter-wrap it forward over the mohair in 4-5 open turns and tie off.
Pick out the mohair fibers with a bodkin or brush, sweeping them back and down so the fly gets a fuzzy, translucent halo.
Build a small thread head, whip finish, and add a drop of cement.
Other versions
3 more in the app: Fly Fish Food Tie, variant 1, Fly Fish Food Tie, variant 2, Beadhead.