Honestly, this is surprisingly difficult even if you 100% agree and are trying to do this (which is true for me). Small children learn what matters and what doesn't matter from us, so if we pay attention to our phones then that obviously signals to them that this must be something really interesting and important.

My partner and I have a child of 20 months and she sees us look at our phones all the time. So she is extremely curious about it, and upset quite often that she's not allowed to do so. And recently I bought a smartwatch so whenever she's on my lap she tries to play with it.

So far our best solution is to have occasional video chats with the grandparents and other family members, which I think is not against the spirit of this advice since it's a healthy, social activity together. At least that teaches her that the phone is meant to be a tool for connecting with actual human beings.

I've also made sure that I don't play games in front of her, but that's relatively easy compared to breaking my other phone habits.