Will God allow people to add their own works to what He has done for salvation?
No. God will not permit anyone to add human works to what He has done for salvation. He has said He has done everything needed, and adding to it would make Him a liar and go against His nature. Justification comes to the one who believes in Jesus, not to those who say they must do this or that.
Les teaches that God is not going to stand for any human being to add to what He has done, because it goes against His nature and would make Him a liar. If God says He has done everything needed for salvation, and a person then says, "But I have to do this or that," that is adding to His finished work. Les says he hopes it is not that serious, but he does not think God can bend, since God has given us His Word and said He has done it all. On the basis of God's Word, a person is on thin ice to say he must do such and such in order to have salvation, because that is just not in Scripture. Justification comes to the one who believes in Jesus, which Paul connects to His death, burial, and resurrection. In the same concept of reconciliation, God will do whatever the sinner needs done on his behalf to bring him back to Himself, and reconciled believers now have a ministry of reconciliation.