They must be generated. Hand designed levels probably wouldn't have things like pawns on the first rank, or four opposing rooks, or situations where the first move unavoidably loses points.
There must be a 'relative position' though in the mix of the algorithm, because on some levels the pieces are scattered in the four corners and some others they are on 'perfect-knight-stepping-sequence' so I could take 5-6 pieces in 5-6 moves and then exit.