Maybe 2 minutes normally. Hard to tell really. If I don’t I have two strategies:
If I’m staying awake because of some captivating train of thought (stressfull or exciting or whatever) I mentally put it aside with the thought “I can’t change that right now anyway I can deal with it tomorrow” and start trying to freely associate without focusing on any thought starting from some nice landscapes.
Otherwise if there isn’t something obvious keeping me from sleep, I just start focusing on relaxing bodyparts and breathing deeply and slowly to stimulate my parasympathetic nervous system. That normally puts me out quickly.