For what it may be worth, since I am not overly skilled, particularly at the traditional "diagonal stitching" method, and do leatherwork only for personal use anyway, the method I have settled on for a holster toe plug is to sew a narrow strip of leather to the inside bottom edge before sewing up the side seam of the holster, which results in an inner "ledge" inside the bottom opening, against which a snug-fitting plug can be seated, from the top. No need to glue it or otherwise secure it in place, and the thickness of the "ledge" conceals any slight gaps which might result from the plug not exactly conforming to the inside contour of the holster end. Of course the "ledge" gets dyed/contoured/polished for a finished look ...