The municipality primarily encompassed the two islands of Flostaøya and Tverrdalsøya and about 9 square kilometres (3.5 sq mi) on the mainland just north of the islands including the villages of Eikeland, Borås, and Vatnebu.

[6] During the 1960s, there were many municipal mergers across Norway due to the work of the Schei Committee.

Later, on 1 January 1992, Moland (including the area of Flosta) was merged into the municipality of Arendal.

[6] The municipality (originally the parish) is named after the island of Flostaøya (Old Norse: Flóstr) since the historic Flosta Church was built there.

[8] The municipal council (Herredsstyre) of Flosta was made up of 13 representatives that were elected to four year terms.