William Tappan Thompson is not infrequently referenced as the "creator" and "designer" of the Confederate States of America (CSA) national flag in popular media, see William Thompson Designed the Confederate Flag Explicitly as a Racist Symbol by Daniel Miessler, William Thompson, The Confederate Cause, And The White Man’s Flag.
It appears that Thompson was able to convey his opinion as to the design and purpose of the CSA national flag to the public due to his position as editor of the newspaper Daily Morning News (Savannah, Georgia) which later became the Savannah Morning News.
The idea of Confederacy was expressed unequivocally by CSA Vice-President Alexander Stephens
Our new Government is founded upon exactly the opposite ideas; its foundations are laid, its cornerstone rests, upon the great truth that the negro is not equal to the white man; that slavery, subordination to the superior race, is his natural and normal condition.
Thompson's ideas were in accord with Stephens', as can be found in Thompson's writings as to the purpose of the CSA national flag. Although there is some historical debate as to the significance of Thompson's role in actually designing one or more of the national flags which the CSA adopted, his published works relevant to the CSA national flag survive.
It should be noted here that the practical purpose of the (re)design of the flag appears to be the issue of the prominence of the color white being mistaken for the sign of surrender by the army
Our idea is simply to combine the present battle-flag with a pure white standard sheet; our Southern Cross, blue on a red field, to take the place on the white flag that is occupied by the blue union in the old United States flag, or the St. George’s cross in the British flag. As a people,we are fighting to maintain the Heaven-ordained supremacy of the white man over the inferior or colored race; a white flag would thus be emblematical of our cause.
While we consider the flag which has been adopted by the Senate as a very decided improvement of the old United States flag, we still think the battle-flag on a pure white field would be more appropriate and handsome. Such a flag would be a suitable emblem of our young confederacy, and, sustained by the brave hearts and strong arms of the South, it would soon take rank among the proudest ensigns of the nations, and be hailed by the civilized world as THE WHITE MAN’S FLAG.
As a national emblem, it is significant of our higher cause, – the cause of a superior race, and a higher civilization contending against ignorance, infidelity, and barbarism. Another merit in the new flag is, that it bears no resemblance to the now infamous banner of the Yankee vandals.
If disambiguation is necessary to distinguish between the "Rebel" flag or other terms used to describe the contemporary "Confederate" flag, kindly do so within the text of the answer.
Did the Confederate States of America ever officially adopt any of the descriptions of William Tappan Thompson as to the national flag of the CSA?