A method for providing an ordered polymer layer at a surface of a substrate includes depositing a self-assemblable polymer layer directly onto a primer layer on a substrate to provide an interface between the self-assemblable polymer layer and the primer layer, and treating the self-assemblable polymer layer to provide self-assembly into an ordered polymer layer, such as a block copolymer, having first and second domain types at the interface. The primer layer is adapted to improve its chemical affinity to each domain type at the interface, in response to the presence of the respective domain type in the self-assembled polymer at the interface during the self-assembly of the self-assemblable polymer layer into the ordered polymer layer. This may lead to reduction in defect levels and/or improved persistence length for the ordered polymer layer. The method may be useful for forming resist layers for use in device lithography.