An understanding of the finished work and salvation by Grace are intertwined. The only way a holy God could even associate with people like us or like Noah, Abraham or anyone in the Bible was based on the fact that He had preplanned to forgive us... if we let Him do it.
"For all have sinned and fall short of the glory of God, and are justified by his grace as a gift, through the redemption that is in Christ Jesus, whom God put forward as a propitiation by his blood, to be received by faith. This was to show God's righteousness, because in his divine forbearance he had passed over former sins. It was to show his righteousness at the present time, so that he might be just and the justifier of the one who has faith in Jesus." Romans 3:23-26 ESV
Before the cross He looked past sins to Jesus the justifier of mankind and after the cross He does the same thing. God was banking on Jesus' death, burial and resurrection when he saved Noah, Abraham, David, Joseph and everyone else.
"The times of ignorance God overlooked, but now he commands all people everywhere to repent, because he has fixed a day on which he will judge the world in righteousness by a man whom he has appointed; and of this he has given assurance to all by raising him from the dead." Acts 17:30-31 ESV
The word there 'overlooked' also translated 'winked at' in the KJV is only used once in the NT. It is Hyperorao (Strong's G5237). It means to interpret something by something else you see beyond it. God looked beyond past ignorance because He saw Christ in the picture.
God commands that all people do this also. He wants everyone to look beyond their own thought and see Jesus. The only way to properly interpret our lives is by seeing Him. Seeing Him in the context of the finished work is an unobstructed viewpoint. From there we see Him clearly from outside of time and circumstances.
'On Christ the solid rock I stand. All other ground is shifting sand. All other ground is shifting sand.'
Grace is the only way anyone is ever saved. One false claim that people make is that because all sins are paid for then all people are equally related to God. Everyone must then be saved because sin was 'the problem' and it is taken care of.
Sin is taken care of. But sin killed us. It killed us each individually. A full pardon does not do a dead man very much good.
"So you also must consider yourselves dead to sin and alive to God in Christ Jesus... Do not present your members to sin as instruments for unrighteousness, but present yourselves to God as those who have been brought from death to life, and your members to God as instruments for righteousness." Romans 6:11, 13 ESV
"For what does the Scripture say? 'Abraham believed God, and it was counted to him as righteousness.' " Romans 4:3 ESV (also stated in Galatians 3:6 ESV & James 2:23 ESV)
In Christ we are spiritually raised from the dead to enjoy a new life. Grace saves us from what we have done and what those things have done to us. It saves us from being trapped in what anyone else has done to us also. Believing in Jesus is the key. Seeing what He has done and believing.
"Giving thanks unto the Father, which hath made us meet to be partakers of the inheritance of the saints in light: Who hath delivered us from the power of darkness, and hath translated us into the kingdom of his dear Son" Colossians 1:12-13 KJV
God could move us from one place to another because of a cross... because of the One who hung on the cross but is alive forever. God can look at us because He looks beyond us and sees Him.
Today we can see ourselves correctly if we look beyond ourselves and see Him. We can look at others correctly by picturing Jesus standing near them waiting to be gracious to them. It is not just our imagination. He Is close by... He is in the picture. We can only see that if we look by faith and not by sight.