I have no earthy idea, but! I have a few thoughts to share!..
plan #1: (no clasp)
I would string and knot the cord to the appropriate length for both sides, less the lariat portion, and call one end A, and the other B (I would leave 3-5 pearls at the end of end B un-knotted.
then taking end A, go thru the biwa, and then string the lariat portion (no knots, perhaps short cords tied in between each bead as a temporary knot spacers) and go around the bail/ clasp whatnot, and then double back…now knotting between the pearls on the lariat portion
then thru the biwa again (perhaps a second hole path was drilled)
and then double back thru end B, thru the 3-5 un-knotted pearls, now knotting them
cut the end and glue…
this plan assumes a long necklace, with no clasp…
plan #2: (back clasp)
string thru 3-5 beads (not knotted), then around the clasp, and back thru the 3-5 pearls, now knotting in between.
cut the loose end and glue
string and knot the rest of side A
-go thru the biwa pearl, and string the lariat portion (not knotting), and then double back up the lariet, now knotting, and back thru the biwi pearl.
then string and knot side B up to the end, leaving the last 3-5 pearls un-knotted (no knots, perhaps short cords tied in between each bead as a temporary knot spacers) and go around the bail/ clasp whatnot, and then double back…now knotting between the last 3-5 pearls.
cut the end and glue
this assumes that you can fit the cord to double back thru the 3-5 end pearls…I usually will drill the holes larger to accomodate double the cord(s) thickness…