Wood anatomical analysis is a fundamental tool in dendrochronology, ecology, and plant physiology. An important preparatory step is the splitting of wood cores into smaller segments that fit glass slides and standard histology cassettes for microtomy and imaging. Manual splitting, however, introduces variability in segment length and cutting angle, which can compromise sample orientation for transverse sectioning. This process could also present safety risks. To address these limitations, we designed and fabricated a specialized, low-cost 3D-printed jig—a miter box for wood cores. This tool standardizes the splitting process by ensuring consistent segment length and a precise 35-degree cutting angle respect to the core lengths. It also improves user safety by securing the core and minimizing direct contact with the cutting blade. This accessible solution enhances the efficiency, reproducibility, and safety for high-throughput sample preparation in wood anatomy laboratories with basic 3D printing capabilities.