Castling Queen Side against the Slav
In addition to what Ineffaceable said, the slav is a sturdy position for black, it's not something a queenside castle is going to break down rapidly. The d file is not especially vulnerable either, c6+e6 usually create a very firm grip over it, so you don't even gain a tempo in the attack. Infact, your king might just get in the way by blocking the c file, if anything.