Post and core fabrication is important in the restoration of endodontically treated teeth. Significant coronal and radicular dentin destruction commonly occurs in endodontically treated teeth. As a result, preserving all the remaining tooth structure is imperative in order to improve the prognosis of the restorative treatment. Core height and width need to be carefully designed and built in order to receive the final restoration. Direct free-hand composite resin core buildup in increments may be a challenging and time-consuming procedure in the dental chair. The case report presented in this article describes a clinical technique using a clear matrix to receive composite resin injections in order to achieve an ideal shape and core size.