A highly regular assembly of three-sided pyramids can be fabricated by growing the ionic insulator NaCl on the kinked metal surface Cu(532). Only two pyramid faces are covered by NaCl, resulting in an overall surface structure which is modulated in surface chemical behavior. Scanning tunneling microscopy shows that the underlying restructuring mechanism can be attributed to a clear-cut criterion for enhanced interface stability mediated by electrostatic interactions. This criterion provides a generally applicable guideline to create nano- to mesoscopic surface structures by design.