When (and how) do I add a pre-packaged japanese curry to a slow-cooker? Opinions across the internet vary on the most effective time (and method) of adding the curry roux to the slow-cooker.

Is the most optimal means to melt the roux with a little hot water in a seperate saucepan and add it on top of the other ingredients, or is it better to simply break the block up and add it at the end?
Just break it up and add it after the vegetables and any meats are completely cooked. Do keep the curry on the heat, stirring constantly, until the blocks have become thoroughly incorporated but don't let it stay on the heat unattended after you add the curry blocks as the mixture thickens considerably and may burn (guess how I figured that out).