An ultrathin photo-crosslinkable random copolymer film was designed as a substrate-independent imaging layer for block copolymer (BCP) thin films. Negative-tone resist chemistry was combined with the chemistry of neutral surfaces to formulate the imaging layer. The synthesis of the imaging layer, optimization of the photo-crosslinking conditions, and patterning of BCP thin films on the imaging layer is discussed. The mild room temperature crosslinking chemistry is especially attractive for BCPs containing temperature-sensitive monomers.