I've been looking for a good Harry/Lavender fic that's more than PWP. The closest I've found is a scene in Clell65619's "Road Trip", but even that's just a one night stand.
This takes place at Hogwarts, either in the later canon years or in a post-Voldemort "eighth year". If you make it post-Voldemort, Lavender's encounter with Greyback should be addressed but it doesn't have to be prominent. In any event, all the characters are of age.
Wherever or whenever, Harry finds himself talking to Lavender. It can be in a standard social situation (a party, pub, or even a meal in the Great Hall, but if it's a pub they do not get drunk or high).
Lavender is gossipy, shallow and obsessed with divination, but she does not have the boy obsession some fanfics seem to saddle her with. Harry has been in a committed relationship with either Hermione or Ginny, and both Harry and his SO are virgins. In any event, a bed magically appears (not a broom closet), and H&L end up in it naked. Whether they have sex or not, they spend most of the night talking and growing closer.
They may not have a future together in mind, but there has been a connection, and they both have to come to terms with it. This can (and probably should) be M-rated, have fun with lemons if you want but it shouldn't be the story's focus — I'm interested in what happens after.