Lollipop cropping?! When to do it? How many nodes?

I figure I'm going to lollipop half of my plants. I'm still in veg. I was told to do it 2-3 weeks into flower but I don't know how accurate that info is.

How many nodes from the top do you leave on?

Does anyone have any relevant pictures on how to do this properly?

Can anyone chime in on this?

if you look some were at the end of my thread you will see how i have done it. https://www.rollitup.org/dwc-bubbleponics/448220-continuing-my-grow-here-2.html