Center an approximately 12x18mm oval bead of your choice between 2 triangle spacers on a length of waxed linen cord. Tie overhand knots on each side of the spacers to hold the beads in place.
Add two more equally spaced groupings of the oval beads and spacers on each side of the cord.
Use an awl to help snug the knots against the beads.
When attaching the cord to the eyeglass holders, use two crimps on each side for extra security, with crimp covers for a decorative accent. New to jewelry-making? See Basic Jewelry-Making Technique Sheet (PDF) for crimping instructions.