You can do it at the flowering stage. Not sure how far into flowering it's still good for.
I do it from my veg plants. I use a 3gal dwc setup. 3gal bucket, air stone, root hormones, super thrive, and nutes. I just clip and place it right at water level. A week later I get roots. I spray them with water when I have time roughly 2-3 times a day. I don't use a humidity dome like what most people do. So far I have a 100% success rate.