Hi Doug, what you are experiencing with your Clayton with the formation of a big sheet of clinker is the result of your firebox design.. The sloped firebrick sides act like a funnel.. and as the coal burns down and the ash drops through the grate into the ashpan, the very hot pieces of burning coal and ash get funneled together, jammed together while they are HOT, near the temperature where the ash is molten [ash fusion temperature, or AFT] and the pieces of ash fuse togther into a big clinker.. have you noticed that some parts of the clinker look like molten glass?
There is nothing that can be done except maybe redesign the firebrick mounting on the sides so that the bricks are vertical or near vertical.. There is another Clayton owner that found some specialzed firebrick and reshaped his firebox for better antracite burning.
If you look at any of the made-to-burn-coal stoves, like the Harman Mark series, or the Harman SF250, A Harman TLC2000, a handfired Alaska or Keystoker, or a Harman SF 160-260-360, or a Hitzer stove, you will find that the firebrick are vertical.. and the entire floor of the firebox is composed of several grates to grind up any small clnkers.
The Clayton is the best at burning coal of all of the US Stove Co. wood/coal appliances,, but all of them are really meant to burn wood, which doesn't need the square sided firebox,, and then 'also burn coal'.. the word coal was added to the name/description for marketing,, but unfortunately it does have some quirks and problems when buring coal.. You have discovered some of these quirks..
You may have better luck with burning nut size coal, and shaking it less, let the powdery ash around the hot coals insulate them from each other,, keeping them from fusing together. And try burning the stove at a lower heat level, this may keep the clinkers smaller, less of a problem..
As for lighting a single fire for the whole season,, I really do't think you can with that firebox design, unless you can cure your clinker problem. I had to shut down my 'Big Bertha' stove which has a similar fiebox design every week to remove the clinker that blocked the grates..
It's good to hear that your Clayton burns well, often the US Stove products have problems with the fire going out, or poor heat output.. At least you have the best of the US Stove products.. the 'hot blast' and a few others are pretty problematic for the owners.