Another way is if there was a magical accident that forces Harry and Snape to rely on each other. For example, they are trapped in a magical realm where only by combining their unique magical abilities can they escape. During this time, they have to put aside their differences and work together. Harry learns about Snape's past traumas and Snape sees Harry's courage and determination up close, which changes their relationship for the better.
For Harry, you can explore his more mature side. Since he has experienced so much in the original series, in the fanfiction, he can be shown as more confident and less impulsive. He could also be more empathetic towards Severus, given Severus' difficult past. For Severus, his dry sense of humor and his deep - seated loyalty (even if it's hidden) can be further explored. Maybe show how his relationship with Harry changes his view of the world and makes him a bit more open.
The relationship would start off rocky. Snape would be resistant to Harry's kindness as he has always seen Harry as James Potter's son. But Harry's persistent efforts to understand and help Snape would gradually break down Snape's walls.
For Snape, his usually cold and strict personality could be enhanced in his dominant role. He might be more demanding and less patient. Harry, as the sub, could develop a more submissive side to his usually brave and headstrong personality. He would learn to listen more and be less impulsive.
One idea could be a story where Harry, under the influence of a powerful spell, has to live a day in Severus Snape's memories. He gets to see Snape's childhood, his unrequited love for Lily, and all the sacrifices he made. This would give Harry a new perspective on Snape.
The relationship can start with conflict. For instance, if Harry is in a position of power over Draco, Draco might resist at first. Then, through shared experiences like facing a common enemy or solving a mystery together, they can start to understand each other better. Harry could show kindness to Draco, which Draco may not be used to, and this can gradually break down the barriers between them.
One idea could be a time - travel plot where Harry, through some magical mishap, travels back in time and ends up having to work closely with a young Severus Snape. They could start off as enemies, given their future relationship, but as they face common threats in the past, they gradually develop an understanding of each other.
It would be extremely complex. Harry might initially be in disbelief and struggle to accept Snape as his father. Snape, on the other hand, would probably be very strict but also deeply protective in his own way.
A possible way to develop their relationship is through a magical owl - related research project. Hermione, being the studious one, is eager to participate, and Snape is in charge. As they work on the project, they exchange ideas and arguments. Over time, Hermione starts to respect Snape's vast knowledge, and Snape begins to appreciate Hermione's fresh perspectives. This could transform their relationship from a hostile one to a more amicable one.
One key element is the power dynamic. With Harry being sub and Snape dom, it creates an interesting relationship where Snape's authority and knowledge are emphasized. Another element is the exploration of their characters in a new light. Harry may show more vulnerability, and Snape may display different sides of his personality.
There is also the theme of secrecy and forbidden love. Given the nature of their relationship in the original Harry Potter series, a 'dom Harry sub Snape' relationship in fanfiction is often portrayed as something that has to be kept hidden. This secrecy adds an element of excitement and tension to the story, as they have to be careful not to be discovered by others in the wizarding world who may not understand or accept their relationship.