Severe glenoid deformity with bone loss presents a significant challenge in shoulder reconstructive surgery. In the context of reverse arthroplasty achieving ideal glenoid baseplate position, specifically the maintenance of an appropriately lateralized joint center of rotation, will generally result in a large residual bone defect in these cases. Addressing this with primary structural bone grafting from the humeral head is a reliable treatment option with the advantage of restoring bone stock. Shaping and fixing the graft can be a difficult, time consuming, and somewhat inaccurate process of trial and error. Achieving optimal glenosphere position and fixation is also challenging due to the limited bone stock available and disorientation due to anatomic deformity. We present a novel bone graft preparation technique that allows expeditious ex vivo graft fashioning using a custom 3-dimensional plastic model of the glenoid as a template. In our series of 7 shoulders, integration of humeral head autograft was noted in all shoulders at a mean follow-up of 16 months. Patient-specific instrumentation is utilized both to construct the model and ensure optimal positioning of the glenoid prosthesis and the graft.