Knotless box braids solved the single biggest complaint about traditional box braids: the tight little knot at the root where the extension hair gets tied in, which is exactly where the scalp tension and post-install headaches come from.
Instead, the technique starts with a small feed-in braid of your own hair, then adds the extension hair gradually — the braid grows into its full thickness instead of starting there, which is also why the front rows lie flatter and more natural along the hairline.