When did the triune God come together before creation?
The triune God came together in eternity past, before anything was ever created. At that determining council, the triune God laid out the plan of the ages, including the coming of Jesus of Nazareth to Israel and Israel's rejection of their King. It was a meeting of minds, not a lengthy debate.
Les explains that Acts 2:23 describes Jesus as delivered by the determinate counsel of God, which he renders as the determining council. He illustrates this as a meeting of minds, like a president calling his cabinet together for counsel. Les teaches that the triune God held such a council someplace way back in eternity past, before anything was ever created. They did not have to sit there all afternoon batting this back and forth; nevertheless, at some time in the past they came together and laid out the whole plan of the ages. That plan included the coming of Jesus of Nazareth to the nation of Israel and the nation's rejection of their King.
Him, being delivered by the determinate counsel and foreknowledge of God, ye have taken, and by wicked hands have crucified and slain: