How does Les say God makes himself visible in Christ?
God makes Himself visible in Christ by Christ being the image, likeness, and physical appearance of the invisible God. Christ is the visible manifestation in the flesh, bodily, of the invisible God, so the Son reveals Him in physical form.
Les teaches that verse 15, speaking of the Son in verse 13, identifies the Son as the image, the likeness, and the physical appearance of the invisible God. He says, "That's what Christ is." Christ is the visible manifestation in the flesh, bodily, of the invisible God. So God, who is invisible, is made visible in Christ by the Son's physical, bodily manifestation.