Secure the Niihau shell on a folded cloth or soft pad
Mark the exact spot where the hole will go
Use a very small diamond drill bit or shell drill bit
Wear eye protection and a dust mask
Keep the shell and bit wet with water while drilling
Drill at very low speed
Apply light, steady pressure only
Stop frequently to re-wet the area and clear dust
Drill from one side until nearly through, then finish gently
Support the shell from underneath to prevent cracking
Clean the hole with water after drilling
Let the shell dry completely before handling further