Make 6 spacers from beads and place them on the bead jig as shown here. You can make a bead jig with wells for the spacers but as you can see in the top picture, it is not necessary to have extra wells. Place the spacer beads so that when you insert a threading rod through a row of beads, the spacer is the first bead the threading rod goes through.

If the spacer beads come off the thread when you are transferring them to the rosary cord, notice where the slit in the bead is and hold the bead so that the thread does not slip through the slit.

Make the spacers from a bead of a color that will be different from the beads you use to make the rosary so that you will not forget to remove them.