One popular 'ed x al fanfic' might be 'The Brothers' Bond'. It focuses on the deep emotional connection between Ed and Al. Another could be 'Adventures Beyond the Gate' which takes their story in a new and exciting direction.
There are also fanfics that explore alternate universes. In these, the relationship between Ed and Al could be different from the canon. Maybe they are in a world where alchemy works differently, or they have different personalities. This allows for a lot of creativity in exploring their relationship in new settings and scenarios. It can also lead to different interpretations of their bond, whether it becomes more strained or even closer in these alternate worlds.
Another way is to follow fanfic authors who are known for writing 'ed x al' stories. They often link to other great works in the same genre or by their friends. Also, check out fanfic review blogs. They sometimes feature 'ed x al fanfic' and can give you an idea of which ones are worth reading.
Winry would be a great addition. She has a deep connection to Ed and Al, and her skills as a mechanic could play an important role in the story. Another good character is Roy Mustang. His military power and knowledge of alchemy could add a lot of drama. He could be either an ally or an obstacle depending on the plot.
One possible aspect to consider in this fanfiction could be the character development of ED and AL. Their relationship in the original series is very deep and in the fanfiction, it might explore new dimensions of their bond, perhaps in different scenarios or alternate universes.
You can try fanfiction.net. It has a large collection of Fma (Fullmetal Alchemist) fanfics involving Ed and Al. There are often filters you can use to narrow down your search to just the stories that interest you most.
One popular 'baby ed and al fanfic' might be those that explore their early days of alchemy training. For example, a story could focus on how they first discovered their interest in alchemy and the small experiments they did as children.
The fanfiction might introduce new storylines that are not in the original series. It could be something as simple as a day in their lives that was never shown before, or a more complex plot involving new villains or challenges. And seeing how ED and AL react to these new elements is part of the allure.
To make it a good 'baby ed and al fanfic', include some elements of alchemy in a way that is accessible for their young age. Maybe they discover a simple transmutation circle and try to figure out what it does. Also, don't forget to add some emotional depth, like their bond as brothers and how they support each other even as little kids.
One idea could be a story where Ed and Al find a way to reverse their alchemical mistakes in a completely unexpected way. Maybe they encounter a long - lost alchemist who has a unique method. Another plot could be them traveling to a parallel universe where their roles are reversed. For example, Al is the one who is more assertive and Ed is more reserved.