A requisite for successful nanopatterning is a precise interface control to meet the adequate surface energies. In block copolymer (BCP) nanopatterning, the interfaces need to be neutralized, promoting both blocks to wet the substrate, and thus realizing the perpendicular orientation of BCPs. However, conventional methods for surface neutralization are expensive and require complex multi‐step processes, which hinders the application of BCP to continuous lithography processes. In this study, the simplest method for controlling the out‐of‐plane domain orientation using frustrated interfacial self‐assembly (FISA) of BCPs is introduced. The FISA layer is a randomly segregated structure that is readily created from the air/water interface. The FISA layer can be transferred to any target substrate, neutralizing both free and substrate interfaces. Employing FISA, the highly aligned and perpendicularly oriented sub‐10‐nm BCP patterns are produced with exceptional simplicity.