Final answer:
Bones for stock are prepared by blanching, browning, and sweating to enhance their flavor in stock. Sweating involves gently cooking the bones in fat until they release their moisture and become slightly browned.
Step-by-step explanation:
Bones for stock are prepared by blanching, browning, and sweating. These techniques are used to enhance the flavor of the stock by caramelizing the bones and releasing their natural flavors. Sweating, in particular, involves gently cooking the bones in a little bit of fat until they release their moisture and become slightly browned. This technique is commonly used in French cuisine to add richness and depth to stocks and broths.