If you are referring to the same "Little Black Stone" as we have in the East, it's nothing more than a diminutive black stonefly nymph tied in sizes 14, 16 or 18 (depending on river). Deadly as all get out, too, and the GL Steelies love 'em.
Unfortunately, hard to land many due to the small hooks.....
Just use your favorite stone fly recipe, but reduce the size, and use all black material.
Anyway, walking along a snowy stream bank, look for evidence of LOTS of shed cases. Very common late winter-early spring occurrence.