Posted: 17/09/2016 at 07:24
I would put a layer of grit in the bottom of the planter to stand the plants in pots on. They shouldn't need much watering. As long as they don't dry out they'll be ok. Inspect regularly for slugs and snails who think you've provided winter bed & board for them.
Put the window on top but with a gap between it and the top of the container to ensure plenty of air flow and on dry and sunny days prop it open, closing it before sundown. The danger with cold frames is lack of air flow which can cause the plants to rot.
If strong winds are forecast tie or weight the window down.