I'm going to try to answer this question for you. I put cardboard, grassclippings and a load of dirt down in one of my beds 2 yrs ago. I didn't turn it under, you don't need too.It will breakdown into the soil, so there is no need to turn it under. I've not heard of using clover, Is it growing in the bed? If so and you don't want it any longer, you could put news paper down and put mulch on top of it. If you turn everything under, how do you keep from disturbing you winter sown plants. The cardboard is the best thing I've found for killing the grass in a bed. I used to use news paper, sometimes I still do. But the cardboard is easier to work with. I got lots of "she's crazy" looks from my neighbors too. Hope this helped.
Jennie