Bantu Knots

I'm officially stumped when it comes to Bantu knots. I've tried them on wet hair, damp hair, dry hair, freshly blowdried hair, even freshly flat iron sections thinking the heat from the flat iron would help the knots set. Every single time, my style falls flat, literally. As soon as I take the knots down I have awesome big beautiful curly waves then about 10 minutes later it's a loose wave and an hour later forget it my hair barely has a bend it in. I'm not sure what gives! I feel like I've tried everything from different methods, to different products, to loading up on hair spray (which I hate) and nothing works.

So my question... Relaxed Ladies, how are you getting your bantu knots to last?