I use clay and horse manure in my raised beds. New Beds, I start by spreading the manure on the ground and then mixing it with the clay soil by using a rototiller. I fill the bed with pure horse manure and then mound the mixed soil and manure over the horse manure in the bed.
During the growing season, the mounded dirt drops below the top of the bed as the manure under it compost away. The composting manure provide the fertilizers and heat that makes the plants grow green and healthy.
The second year and each year after, I shovel all the dirt to one end of the raised bed. Fill the empty end with manure and then shovel the dirt back over the manure, then do the same with the other end of the bed. When done, I have the compost dirt mix from the previous year mounded on top of the fresh manure and it starts over.