Computer-aided design and manufacturing (CAD/CAM) have improved the accuracy of genioplasty; however, complex three-dimensional movements such as the “Tetris genioplasty” remain surgically demanding. This technique requires precise trimming of bony interferences to achieve a perfect “lock-and-key” fit, which is difficult to perform freehand. We present a novel three-step digital workflow to address this challenge. Our protocol utilises a novel Intermediate Trimming Guide (ITG) designed to precisely resect specific bony interferences on the mobilised segment. In this case with facial asymmetry, the ITG successfully converted visual estimation into a guided, demonstrably accurate surgical step. Superimposition of the planned and postoperative CT models demonstrated sub-millimetre accuracy (root mean square error < 1 mm) between the simulation and achieved position, alongside successful autologous bone recycling. In this preliminary case, this workflow appeared to simplify the complex trimming of the “Tetris” block, potentially facilitating more predictable outcomes for asymmetric genioplasty.