Normally hutches have wood on the bottom and are raised off the ground with legs for warmth and security. You would ideally put a protective layer on top of the wood such as a sheet of plastic, Lino or Correx to protect the floor from urine
A run is normally made with wood and mesh but is open on the bottom so piggies can get to the grass. The advice is that they are not left in a run while you aren’t there to supervise them and not left in it over night. If the climate is wet in NZ, they also cannot be on grass during any wet/colder times. Instead they would be moved back to the secure hutch.
As you have a young trio of boars, and if you were to build a hutch with a separate run then you need to make sure both a hutch and run cover at least three square metres each and are able to be divided if the piggies need to be separated, with any potential pair which can be made after a trio separates still having a 180x60cm space in the hutch (the recommended size for a boar pair).
if you want them to free roam, then having then live in a fully wooden shed (with a wooden floor) is a safer option for security and warmth and also provide a trio with enough living space. Again with a separate run on grass and the ability to divide the area al they can be split up
