Complex sentence: In the years after the end of the American Civil War, many former slave states that were members of the Confederacy adopted new state flags incorporating in their designs motifs that were used in the Confederacy's flags.
Split into simpler sentences: In the years after the end of the American Civil War, many former slave states that were members of the Confederacy during the war adopted new state flags. Incorporating in their new flags'designs were motifs that were used in the Confederacy's flags.