Abstract: A computer-implement method for forming a flow insert for an ultrasonic flow meter. The method includes positioning one or more reflectors in a flow insert cavity configured to receive plastic by injection molding and configured to define an ultrasonic signal path based on machined surfaces of the mold and fixing the one or more reflectors in position along the ultrasonic signal path extending into the flow insert cavity. The method further includes forming a flow insert body by injection molding and configured to define an ultrasonic signal path within a flow conduit that includes one or more reflectors integrated within the flow insert body during the injection molding and providing ultrasonic signal reflection along the ultrasonic signal path.