Turned this up in a bit of late research for a minor part of Griswoldville.
The novel's protagonist, young Georgie Wax, is consumed with knights and medieval stories and takes a keen interest in heraldry as a result. After being called up to the Georgia militia, he passes hours of boredom trying to create a blazon—or official, formulaic description of a coat of arms—for his unit's battle flag.
This was my favorite. The three colors of red, white, and blue were preserved in it. It avoided the religious objection about the cross (from the Jews and many Protestant sects), because it did not stand out so conspicuously as if the cross had been placed upright . . .
Besides, in the form I proposed, the cross was more heraldic than ecclesiastical, it being the 'saltire' of heraldry, and significant of strength and progress (from the Latin salto, to leap). The stars ought always to be white, or argent, because they are then blazoned 'proper' (or natural color). Stars, too, show better on an azure field than any other. Blue stars on a white field would not be handsome or appropriate. The 'white edge' (as I term it) to the blue is partly a necessity to prevent what is called 'false blazoning,' or a solecism in heraldry, viz., blazoning color on color, or metal on metal. It would not do to put a blue cross, therefore, on a red field. Hence the white, being metal argent, is put on the red, and the blue put on the white. The introduction of white between the blue and red, adds also much to the brilliancy of the colors, and brings them out in strong relief.
Blazon, saltire, azure, argent—heraldry relies on a vast, arcane vocabulary of largely French origin in a convoluted and rigid syntax meant to preserve the design of a given coat of arms with the permanence of a molecular formula.
Thus, the flag of England is Argent, a cross gules and the flag of Scotland is Azure, a saltire argent. And these are simple blazons. Entertain yourself sometime with more complicated ones.
So here, as a special first look at Griswoldville, is what Georgie comes up with:
Gules, a saltire azure charged with thirteen mullets argent. I was unsure how to account for the fimbriations, the white borders of the cross, and occupied myself for hours sometimes in shifting this subordinary back and forth through my primitive blazon.
It's worth pointing out that the commonly repeated bit of lore that the flag's design stems from the St. Andrew's Cross of Scotland, because of the vast sea of Scots-Irish farmers who supposedly formed the backbone of the Confederate Army, doesn't enter into it. Just good, sound artistic principles within a body of established tradition here—with a few politico-religious considerations thrown in.
Miles's concluding paragraph to Beauregard begins with my favorite line in the letter: "But I am boring you with my pet hobby in the matter of the flag." What amateur vexillologist hasn't said some version of this?