Instead of making a collar card that would be cute for Father's Day, I cut the collar on the side to make a birthday card. To make the collar, score your layer from the right side to the center of the card , and then cut on the score line. Fold the cut sides back and and then decorate your card to suit the occasion.
They are easy to make, and if you wanted to make one for Father's Day to represent a shirt collar, just do the same but score and cut on the top of your layer instead of the side.
The following were used: