Specifically No Cessna 150,152,172 model is placarded as "no slips with flaps". The limitations section of the POH for all models of Cessna 150, 152,172 does not contain a limitation prohibiting slips with flaps deployed.
I'm not an instructor but it's surprising how many people think you can't slip a 172 with flaps extended. Another old chestnut is to drop 10 degrees flap for a short field t/o in a 172. No, you don't.