Update:
I've really been trying to keep the faith. After Ted's recommendation I did a few runs in the traditional lacing style and still struggled, especially with the heel straps falling down. I went back to my old lacing style for a couple runs but then examined some pictures on-line after searching "tarahumara huaraches" and noticed something.
It's obvious the way the straps are coiled around the ankle is top-down. On the Luna site they demonstrate coiling bottom-up:
https://lunasandals.com/pages/how-to-tie-traditional-luna-sandals
That makes for a key difference. When coiliing bottom-up the final length that gets tied to the thong strap comes down from higher up. Coiling top-down the final length comes at it from a lower angle. This means the knot is at the end of a length laying flat on the foot rather than suspended up and I get less pressure focused right at the knot. Over the last couple of weeks this has been a lot nicer to my skin!
One last problem: heel strap slippage. It didn't matter how tight I got the straps the heel strap kept falling. Very annoying. I was tying things so tight my outer ankle tendons were a little tender. Still the heel strap kept falling. I figured that couldn't be right.
Today I tried something different: I laced them up just like how Manuel Luna would: coiling top-down, knot on the thong strap and no naughty deviations. The only correction was to make an assumption that has always improved my running:
must be a running form problem. The more humble I am about my own running form the better and I've never gone wrong assuming I don't know WTF I'm doing with some part of my stride.
So, if my foot slides forward in the sandal the heel strap gets loose. That means it can slide down easy. My foot shouldn't slide forward in the sandal while running because if it is
I'm over-striding! Even if the over-stride is slight it's still not good. That old, familiar, hateful braking move I keep lapsing to. Even after 7 years of minimalist and the last several of unshod that damn over-stride still tries to creep back in and screw me up.
Today I focused on keeping the pressure of my foot back against that heel strap. I even laced up the sandals a bit loose. The leather stretches out a bit after a few miles and once I stopped to dig out a rock that wouldn't kick free I noticed I could slip that heel strap down easily with a finger. But during the run: no heel strap slippage!
I focused on the idea of "scratching back lightly with each step" as I believe Caballo Blanco once described the Tarahumara's feet doing during Leadville in 1994 in
Born to Run. It really seemed to work and my pace was even a bit quicker than it had been for my runs this year. I'm not officially tracking my pace but I do cheat just a little and noted the time at mile markers. Quicker pace, easier running, no heel strap slippage and my feet also weren't hitting the rocks in the gravel as hard as they have been this season. All good signs that I'm finally not being a dumbass and doing something right!
If anybody else has been struggling with huarache sandals' heel straps slipping when sticking to "traditional" lacing styles try this out. Modern athletic shoes with their snug fit and excessive traction really did a number on me for decades teaching that horrible habit of over-striding. It seems I'll always be fighting against the urge to land too far ahead of me. If that sounds like you and you haven't yet tried huarache sandals give this some thought. There always seem to be new ways I'm finding that they can help improve my running.