How long before Abraham was the flood?
The flood came roughly 400 years before Abraham. The timeline places Adam at 4004 BC and Abraham at 2000 BC, and backing away from Abraham about 400 years in round figures brings us to the time of the flood, which is therefore approximately four centuries earlier.
Les explains that he likes to divide the timeline in round terms so it can be remembered. He starts with Adam's creation at 4004 BC, then places Abraham at 2000 BC, halfway between Adam and Christ's first advent. From Abraham, backing away about 400 years in round figures brings us to the time of the flood. Les notes this isn't in exact years, but it gives a memorable framework: the flood is roughly 400 years before Abraham.