The problem with all these proposals is that the loop is in the wrong medium, it will cut through and the coating will tear off the fly line. Make a self loop in braided monofil, secure it with a dab of superglue. Slide the tapered end of the fly line into this and secure the same way. No salmon or trout has ever given my joint a reason to be doubted.
If you must put a loop in fly line then make a 12" loop of any old line, hook it over the vice handle or any handy projection, thread the end of the fly line through it and holding it taut aganst the vice handle,start whipping FROM THE LOOP END. This makes coming off the taper easier. Use waxed rod whipping thread,when finished roll it between two smooth surfaces to straighten the curve of the splice and varnish or superglue.Then cut off the old line loop.