Correct way to solder headers to D1 Mini Pro

I have a D1 Mini Pro which was supplied with some headers but they were not soldered on. What is the correct way to solder on the header so that I can attach daughterboards, hats etc, to it? If I use the headers with long solder tails, then I can presumably attach daughterboards on both sides of the CPU. But should the plastic part of the header be on the component side of the PCB, or the copper side?

Thank you - Rowan

I think it’s a question of personal preference.

The daughterboard will probably also come with a set of sockets/pins that are not soldered yet.

My preference is to have sockets on top of the mainboard (d1 mini), and pins on the bottom of the daughterboard. So the “mainboard” without the daughterboard is mostly electrically safe with as few as possible pins exposed. And I have the daughterboard sitting on top of the mainboard. A bit like how you would put an integrated circuit into a IC socket.

If you’re connecting things up with dupont wire, I prefer to have pins on the mainboard and pins on the other thing, then connect them up with female-female dupoint wires.

My parts bin actually has several wemos d1 minis, some with pins on the bottom, some with pins on top, some with sockets on top.