The insert on their Getting Started guide.
let new_post = NewPost { title, body };
diesel::insert_into(posts::table)
.values(&new_post)
.returning(Post::as_returning())
.get_result(conn)
.expect("Error saving new post")
Of course the other possibility is this guide is very low on abstractions.
One of my main concerns with this is the potential for making a lot of separate calls to the DB for a complex data structure. Then again there are trade offs to any architecture.