There could also be a group of misfit characters. Maybe they are students who didn't fit in at Hogwarts for some reason and found their way to Potter Island. Together, they form a sort of 'found family' and have to work together to face the challenges that the island presents.
One interesting concept could be new magical creatures that are unique to Potter Island in the fanfic. For example, there might be a creature that can change the color of the sky depending on its mood.
His best friends Hermione and Ron would surely visit. They might come to help Harry set up new magical experiments or just to relax away from the hustle and bustle of the wizarding world.
In this fanfic, perhaps Harry could turn the island into a magical sanctuary for endangered magical creatures. He might build a school there for young witches and wizards who are overlooked by the mainstream magical education system.
He might have discovered the island during one of his adventures and claimed it as his own. Since there was no one else on the island at the time, and he was the first to set foot on it and recognize its potential, he decided to make it his property.
Perhaps he uses the island as a secret training ground. He could practice advanced spells away from the prying eyes of Hogwarts faculty and students. Harry might also build his own magical fortress on the island for protection and privacy.
There could be some of the house - elves that Harry has freed. They might choose to live on the island, using their magic to help with various tasks such as farming magical plants or taking care of the island's infrastructure. Also, some of the students from Hogwarts who were inspired by Harry could be there. They might be learning new forms of magic that are specific to the island or studying the unique magical ecosystem there.
Perhaps it's an island with a hidden wizarding school, similar to Hogwarts but with its own distinct features. There might be ancient spells protecting the island, and the architecture could be a blend of different magical styles. Harry could have discovered this island during one of his adventures and decided to make it his own. He might use it as a sanctuary for those in need or as a place to study and preserve rare magic.
The 'island of the slaughtered fanfic' is a rather mysterious title. It might be a fan - written story that centers around an island. The'slaughtered' part makes it seem like there could be a lot of violence, death, or a massacre - type situation. It could be inspired by other works that have a similar dark and violent theme. It could also be that the story has a group of characters trapped on the island and they are facing some sort of threat that leads to this slaughter. Maybe it's related to a specific fandom, but again, without more information, it's difficult to be more precise.
Ron might be there too. He could use his skills in handling magical creatures to populate the island with friendly ones. And he could also help with fishing in the surrounding waters using magic, providing food for those on the island.