I don't make my own strings. (dumb thumbs)
However, I've been using flemish twist strings for 20 years or so. I rarely have the loops "slip" however I have had the ends fray... A few years ago, I started using "Hard as Nails" clear nail polish on all of my new strings.
I string up my bow, make sure the tag ends are laying flat, then put a little drop of polish on the tag ends smooth it out with the brush. I also do the ends of the serving, to prevent any possible unraveling.
I guess you could also put a drop under (or over) your nock point, to prevent fraying and wear.