Asa Flag was born into a farming family in Weld, Maine. He had an older brother with whom he worked in the woods. He worked in the woods for neighbors both in Weld and in Carthage, but also for large companies, where he stayed in camps. He was married twice, the first marriage ending in his wife's death and the second ending in divorce. In 1952, he moved in with his son and son's family's farm in Carthage and continued to work in the woods nearby.