Browning bones in a skillet
Depending on what kind of stock pot or soup pot you intend to use, you can just brown the bones right in the bottom of the pot. I don't think my mom ever put bones in the oven to make soup.

Put a little oil in the bottom of the pot and brown the bones like you would sautee meat over medium high heat. When you've got the desired browning done, just pour in the water you will use to make the stock and boil the bones in the water like you would normally do.