I've been interested in pick-up for quite a while now but I'm still not 100% clear on the concept of a routine stack. I'm generally into natural game or, at least, keeping game as simple as possible but I can't deny that there are times I need some routines to fall back on so I was hoping someone could clarify a few things for me:

I understand that a routine stack is a collection of routines but what's the basic structure of it? Do you have a certain amount of routines and techniques for different phases (attraction, qualification, comfort, rapport etc)?

Are the routines brought in as a means of transitioning comfortably to different phases or to achieving different 'waypoints' (a routine for isolating your target, a routine for k closing etc)?

Are they supposed to flow from one to another or is the ideal situation to maintain normal conversation (adjusted depending on which phase of the pick up you're in) and to only use memorised routines when you're stuck for something to say?

If anyone could help out with these questions or shed any kind of light on the topic it would be a great help. Thanks in advance