(black) string, crisscross the bottom right (red) string through the last bead added.
add one gray, two white beads on the top (red) string, crisscross the bottom (black) string through the last black bead added.
add four white beads on the right (black) string, crisscross the left (red) string through the last bead added.
add one red and three white beads on the top (black) string, crisscross the bottom (red) string through the last bead added.
continue to pass the black string (the one you just used to add new beads on) through one old bead from step 6 marked with a.
continue also to pass the other string (red) through one bead you added 