A method of designing an epitaxy template to direct self-assembly of a block copolymer on a substrate into an ordered target pattern involves providing a primary epitaxy template design and then varying the design to optimize a pattern fidelity statistic, such as placement error, relative to the target pattern by modelling predicted self-assembled block copolymer patterns and optimizing pattern placement as a function of a varied design parameter. In addition to varying a design parameter to optimize the pattern fidelity statistic, a random error in the template design is included prior to modelling predicted patterns in order to compensate for expected template inaccuracy in practice. The inclusion of a realistic random error in the template design, in addition to systematic variation of a design parameter, may improve the template design optimization to render the result less sensitive to error which may be inevitable in practice.