An upscalable, self-aligned patterning technique for manufacturing high- performance, flexible organic thin-film transistors is presented. The structures are self-aligned using a single-step, multi-level hot embossing process. In combination with defect-free anodized aluminum oxide as a gate dielectric, transistors on foil with channel lengths down to 5 mu m are realized with high reproducibility. Resulting on-off ratios of 4 x 106 and mobilities as high as 0.5 cm2 V-1 s-1 are achieved, indicating a stable process with potential to large-area production with even much smaller structures.