Layer-by-layer assembly is widely used for constructing two-dimensional van der Waals heterostructures, yet polymer-induced interfacial contamination in conventional transfer processes often limits device performance. Here, we show that ultraclean chromium oxychloride (CrOCl)/bilayer graphene (BLG) heterinterfaces, realized via a one-step transfer process, enable significantly enhanced electrical modulation. Precise control of the adhesion and release behavior of a polyvinyl butyral support effectively suppresses crack formation and minimizes interfacial residues, yielding uniform and contamination-free heterointerfaces. As a result, directly laminated CrOCl/BLG/boron nitride (BN) devices exhibit an exceptional switching ratio exceeding 10⁸ without post-annealing, outperforming layer-by-layer assembled counterparts by nearly seven orders of magnitude. These results highlight the critical role of interface cleanliness in governing the electrical performance of bilayer graphene heterostructures and provide a robust strategy for high-performance two-dimensional hetero-integration.