The Scripture was Scripture the moment it was penned. The Old Testament did not need to be picked out by Jewish Rabbis and translators in the 3rd century BC or affirmed by the Church in several councils in the 4th century to be AD. Being that God, by His Holy Spirit, wrote the Scripture, whether on not certain books gain universal acceptance does not only then make them Scripture. They always were.
For example, take the Epistle of 2 Peter or the Book of Revelation. Both had serious detractors in the early church. So, even though the majority of the Church accepted them as Scripture before they had universal acceptance in the late 4th century, were they not Scripture in the churches that accepted them?
Of course that would be ridiculous. Saint Clement quoted 2 Peter in both of his letters, which shows that in the 1st century it was considered Scripture.
Now, as Irenaeus lays out when he discusses Apostolic Succession for one of the first times in history, he talks about how things like the Scripture were handed down:
It is possible, then, for everyone in every church, who may wish to know the truth, to contemplate the tradition of the apostles which has been made known to us throughout the whole world. And we are in a position to enumerate those who were instituted bishops by the apostles and their successors down to our own times, men who neither knew nor taught anything like what these heretics rave about (Against Heresies 3:3:1 [A.D. 189]).
From the context, we can see that Irenaeus is clearly not talking about magical apostolic powers inherited by those bishops in the Apostolic churches. Rather, he is saying that the churches which were apostolic all had the same doctrines and traditions, while all the zany heresies he is writing against have not coincidentally originated outside the established churches.
Hence, his contention makes perfect sense. If all the churches which literally received letters from Paul and such (Rome, Corinth, Ephesus, etc) all taught X and had Y Scriptures, but the heretics from totally different places taught A and had B Scriptures, wouldn’t it make sense that X and Y were legit from the Apostles and not A and B?
Therefore, understanding this, we can know that the Tradition always was tradition before a council met and affirmed it. Likewise, the same is true of Scripture.
Hence, the Church did not make Scripture. God did. The Church recognized what God had already done under the direction of the Holy Spirit.