Cut chosen card to 21cm square (an exact square is important). I used double sided pearlescent card approx. 300gsm.
Align your card to form a diamond in the centre of your scoreboard lining the top and bottom corners with the score channel marked 15 cm. Holding the card securely in place, score down in the 8cm and 22cm channels.
Rotate your card 90 degrees and repeat. See photograph.
This will be the right side of your finished project.