Completely detailing now, but I found some great ones this summer that had clearly been designed by someone who actually thought about the toe post + heel issue. It was a low kitten heel with a slingback strap, and a thin strap over the front of the foot near the toe post AND a tbar type strap up the instep. And the sole was cushioned. Result = no flipping, no flopping, no sliding into the toe post.
So that was my summer shoe, and I felt comfortable and smug throughout July and August. Won’t be wearing it for Christmas, mind.