Tom Clemens, Hagerstown Community College professor and scholar writing on the Maryland Campaign, provides a six minute lesson on the six flags of the Confederacy. Actually its the four flags of the Confederacy with one precursor and one modern adaptation.
Here is the the YouTube link to the lesson. Tom's most recent published work is the first of two edited volumes of Ezra Carman’s account of the Maryland Campaign. Here is the Amazon.com link for it.
Image: First National Confederate Flag with the seven stars for the deep South early secession states. This flag was updated by adding stars for the second wave of secession that occurred during April 1861.