Hello Vermonter, does the firebox in your stove have 'V' shaped, sloped sides acting like a funnel to funnel the ash down to a narrow center grate??
Clinkers are formed when the VERY hot coal ash is forced together by either poking the fire when hot, or shaking the fire when very hot.. anything that will cause the fine powdery ash to fall away, and let the super-hot ash to bump into other super-hot pieces of ash will cause clinkers to form The pieces of super-hot ash are molten sand, glass, and other minerals, and they stick together.
In a designed-for -coal firebox, the sides of the box are vertical, and the entire bottom of the firebox is composed of shaker grates... The ash will settle down without the ash being funneled toward the center grate which concentrates the super-hot ash together, creating clinkers.
The best way to reduce clinkers is as berlin said,, build a deep fire, and reduce the amount of shaking... to maybe only twice a day.. you want to be shaking cooler ash at the base of the fire, not red-hot ash that will stick together..
If your firebox is 'V' shaped, you will probably still need to clean clinkers out of the firebox every week or two.
This is what I had to do with my hand feed boiler with a 'V' firebox and central grate.