Per the Clementon Historical Commission, the flag (an image of which is attached) was designed by John H. Fisher, who was a visual artist in addition to being the unofficial borough historian for many decades. He's the man for whom the historical commission museum is named. In his book Clementon: A Historical Outline, which was printed in 1975 for the town's 50th anniversary and again in 1990 for the borough's 65th), Fisher writes:
"In 1972 this writer was proud to have his design for the Borough Seal officially adopted and appear on the borough vehicles and office stationery." (page 74)
So the art wasn't designed for the flag, per se, but made its way there as the town insignia.
If you have further questions or would like additional information on Clementon history, I encourage you to reach out to the Clementon Museum at clementonhistoricalcommission@gmail.com