How do you keep dehydrated broth (powder) from clumping? I have some dehydrated store-bought broth mix (chicken and vegetable) that has clumped into a large solid block. I haven't been able to find any information on the Internet about how to fix this.

I suspect it is a matter of hydration (too hydrated or too dehydrated). I could experiment by adding drying agents/water, but I figured I should ask first before making my broth go funky.
The clumping is a result of air and moisture entering the container with the substance. This especially happens if you pour the mix directly from the container over a hot dish - the steam enters and immediately clumps the spices. What you can do is to transfer your mix into a new dry and airtight container. Hope this helps :)