If you have read my post on shelters for Kunekune Pigs you know that you do not need anything fancy. My first farrowing pen we built was super simple. We used siding panels from Home Depot. The only problem with my first pen is we didn't make it easy for me to get in and clean.
We made the roof way too low and it was very hard to get in there and clean it up. We only put a "crush rail" on the one side and would put the heating lamp over on that side to encourage the piglets to go over there. Millie had all 3 of her litters in here and Panda had her first litter in 2019 using this shelter. In the winter time we would remove the rails and this would just be a normal shelter for everyone. The pigs always loved to pile in there and we would keep the heat lamp on for them. The backside faces the north to keep out the wind. This was the only shelter that we had that was not moveable.
I was getting ready for Panda's 2nd litter in 2020 and decided I was just too old to be stooping inside trying to clean out the shelter plus the chickens had decided it was their new coop and turned it into a big mess. So, I decided to buy some port-a-huts this way we can easily move them around and clean up would be so much easier!
You can also buy crush rails that go all the way around inside. The farrowing huts are 7.5 feet by 5 feet. Our local vendor did not have the crush rails in stock so we ended up building our own. They are about 6 inches off the ground and protect the piglets from getting smashed when momma pig lies down.