To start a fanfic about Naruto and Hinata making Boruto, first think about the setting. You could begin with a simple family scene at home in Konoha. Maybe Naruto is just back from a mission and Hinata is preparing dinner while Boruto is showing Naruto his new ninja moves. Then, start writing down their dialogues. For example, Naruto could be saying how proud he is of Boruto's progress. Keep it simple and build on their relationships as a family.
Well, for starting a fanfic on this, consider their personalities. Naruto is energetic and a bit clumsy at times, while Hinata is shy but very loving. You can start by showing how they interact as parents. Like, Naruto might be too excited about Boruto's training and Hinata has to calm him down. Then introduce the main plot. It could be something like Boruto getting into trouble at school and Naruto and Hinata having to deal with it together.
Start with an idea that focuses on their family bond. Since it's about Naruto and Hinata making Boruto, you could start with a flashback of when Hinata first told Naruto she was pregnant. Then jump to the present where they are discussing Boruto's future as a ninja. Outline the main events you want to include, like Boruto's first big mission and how Naruto and Hinata feel about it. Don't forget to add some emotional moments between them as a couple and as parents.
One plot idea could be Boruto getting lost in a mysterious forest during a training exercise. Naruto and Hinata then team up to find him. Along the way, they face some old enemies or new threats that test their skills and their relationship as a couple. Another idea is that Boruto discovers a hidden power within himself that Naruto doesn't understand, and Hinata has to be the one to bridge the gap between father and son by helping Naruto understand Boruto's new ability.
Websites like FanFiction.net and Archive of Our Own (AO3) are great places to start. They have a large collection of fanfics related to Naruto and his family.
There are many fanfics that explore the relationship between Naruto and Hinata further. Some might focus on their daily family life with Boruto and Himawari, like how they deal with Boruto's rebellious phase while still maintaining a loving family environment.
Friendship also plays a big part. Boruto's friendships at the academy and how his parents' experiences with friendship influence him. Fanfics might show how Boruto helps his friends using the lessons he learned from Naruto and Hinata's stories about their own friends.
To create an engaging Boruto fanfiction, Naruto and Hinata could introduce new elements to the ninja world. Maybe a new type of jutsu or a hidden land with its own unique culture. Naruto's knowledge of different ninja techniques and Hinata's understanding of the Hyuga clan's secrets could be combined. They could make Boruto discover this new element and have to adapt to it. This would not only add excitement to the story but also show Boruto's ability to handle the unexpected, just like his father did in his adventures.
Family could be the main theme. Naruto grew up without his parents, and Hinata has a strong family bond in the Hyuga clan. They could show how important family is in Boruto's life. Boruto might struggle with living in his father's shadow, but his family, especially Hinata's love and support, would help him find his own path.
I don't think there would be a lot of fanfiction like that. Hinata has always been loyal to Naruto. In the Naruto universe, their relationship is based on a lot of development and mutual understanding. So it's hard to imagine a scenario where Hinata would cheat on Naruto with Boruto in a legitimate fanfiction.
There's a fanfic called 'Boruto's Training with Naruto and Hinata'. In this one, Boruto gets special training from both his parents. It delves into how Naruto's teachings differ from Hinata's and how Boruto grows from it. It also has some really cool action scenes where Boruto uses new jutsus he learned from them.
One idea could be to focus on their anticipation and preparation for the baby. They might discuss names, decorate the nursery, and Hinata could be shown getting advice from her family. Naruto, on the other hand, would be excited but also a bit nervous about becoming a father.
One idea could be a story where Boruto and Himawari discover an old diary of Naruto's from his early days as a ninja. Hinata helps them understand the context and the values their father held. They then use those lessons to face a new threat in the village.