Methods and a structure. A first film of a first block copolymer is formed inside a trough integrally disposed on an energetically neutral surface layer of a substrate. Line-forming microdomains are assembled of the first block copolymer, and form first self-assembled structures within the first film normal to the sidewalls and parallel to the surface layer. At least one microdomain is removed from the first film such that oriented structures remain in the trough oriented normal to the sidewalls and parallel to the surface layer. A second film of a second block copolymer is formed inside the trough. Line-forming microdomains are assembled of the second block copolymer, and form second self-assembled structures within the second film oriented normal to the oriented structures and parallel to the sidewalls. A second method and a structure are also provided.