it's very easy to cut the angle of the lap tilted in the wrong direction. if careful attention isn't paid. The radial-arm saw is only one method for milling this joint. It's simple to rout handheld using an angle fence. the table saw also will cut the cheeks of the T-shaped part, aided by a sliding fence jig. Since the end of the T-shaped part aren’t square but angle, the support block on the jig has to be tilted away from the blade to the angle that holds the end of the mitered T-shaped part flat against the table.
Use the table saw miter gauge to steady the work for repeated kerfs across the center lap to waste the material between the shoulders. A dadoing head will waste the center lap material, but watch out for it lifting the part off the table.