Potassium Chlorate is one of the ingredients in Boomerite. I've often fantasized about making it myself because it's the most expensive component, it requires an ATF explosives license to purchase in the quantities I need, and my sole supplier is in New Jersey.
Here is how to make it in your garage/kitchen/basement:
I think I will continue to purchase it. We use about 350 pounds per year and scaling up the process above to meet our needs just doesn't look worthwhile.