Well, in some 'naruto sensei fanfiction', Naruto might be a sensei in a different village. He could be sharing his knowledge of chakra control and ninja ethics with students who have a very different upbringing from what he had. Some stories might focus on the relationships he builds with his students, like a father - figure type of bond. Or perhaps a fanfiction where Naruto has to teach a group of international ninja students, bringing together different ninja cultures under his tutelage.
There are 'naruto sensei fanfiction' that explore Naruto's teaching style. Maybe he uses unorthodox methods, like using his own life experiences as lessons. He could be teaching his students about the importance of friendship and loyalty through his adventures with Sasuke and Sakura. In other fanfictions, Naruto might be a sensei in a more advanced ninja academy, where he has to deal with students who are already very skilled but lack the right mindset. He then tries to instill in them the values that made him a great ninja.
One interesting 'naruto sensei fanfiction' story could be about Naruto teaching a new generation of ninja unique jutsu. For example, he might teach them a special combination of his Rasengan and Shadow Clone techniques. Another could be Naruto as a sensei during a time of peace, and he has to deal with the daily antics of his over - enthusiastic students. There could also be a story where Naruto as a sensei discovers a hidden talent in a seemingly ordinary student and helps that student reach their full potential.