Introducing a neutered Boar (at least 6 weeks post neuter) and sow...
If you are choosing a friend for one of your pigs, requiring one from a reputable rescue will assist with the dating process to ensure the 2 piggies actually like each other enough to spend the rest of their lifes together.
If you are dating the 2 yourself I would let them get at least a sniff of each other other through bars or holding each on an arm. You can gauge the level of interest from there. Usually, young sows are not much of a problem.
You can also have the boar live longside the sow for a few days until their is definite flirting though the bars from both sides. That way, acceptance and a smoother intro is pretty much guaranteed, but in the end how you do the intro does not so much depend on how you do it but whether they take to each other.
You can just put them into a neutral intro pen together with no hidey places, nooks and crannies, tight corners just a big pile of hay and food scattered. What you need to look out for with male/female bondings is mainly aggression from the female when you put them together, only occasionally from a frustrated boar if he is driven to his limits.
Rumblestrut/mounting, and running away, whinning is all OK.
A bonding has failed if there is physical aggression from either side; most likely from the girl's. Failed bondings between neutered boar/sow usually happen within the first quarter of an hour, so you will know very quickly whether things are going to work out or not.
If the boy simply gets ignored or firmly put in his place, this is fine it means sow is nowhere near season and is dominant enough to hold her own.
It will take until she comes into season for the bonding to cememt. Give them plenty of space and no nooks/hideys with one exit when that happens.