Objectives: This study investigates the design, workflow, and manufacture of highly porous, resorbable additively manufactured, 3-dimensional (3D) custom scaffolds for the regeneration of large volume alveolar bone defects. Materials and Methods: Computed tomography (CT) scans of 5 posterior mandibular vertical bone defects were obtained. Surface masks (3D surface contours) of the recipient site were first isolated using a contrast threshold, transformed into 3D objects, and used to guide the formation of custom implant template models. To determine model accuracy and fit, the gap and overlap between the patient geometry models and the idealized template 3D models were quantified. Models were 3D printed from medical grade polycaprolactone (PCL) into porous scaffolds. For scaffold dimensional quantification, scaffolds were scanned using a micro-computed tomography (µCT) scanner. Results: The design and printing processes each achieved dimensional errors of <200 µm on average. The average gap between the template implant model and the scanned scaffold model was found to be 74 ± 14 µm. The printed scaffold was confirmed as having a porosity of 83.91%, a mean polymer or filament thickness of 200 ± 46 µm, and a mean pore size of 590 ± 243 µm. Conclusion: The approach described in this study is straightforward, adaptable to a range of patient geometries, and results in the formation of reproducible, dimensionally accurate custom implants. These highly porous 3D structures manufactured from resorbable medical grade material represent a potentially transformative technology toward the clinical implementation of scaffold-guided bone regeneration procedures.