Diamond Shaped Card

Cut an A4 price of card to measure 14cm x 28cm. (I used a blank square card and trimmed it to 14cm x 28cm with the scored fold at 14cm)
Place the card on your work surface with the short edges across the top and bottom. Using the diagram opposite for reference, mark the left and right hand side of the card 7cm, 14cm and 21cm from the top edge with a pencil.
Score a horizontal line 14cm from the top edge and another 21cm from the top edge.
Score a diagonal line from the left hand 7cm pencil mark to the right hand 21cm score line. Score another from the right hand 7cm pencil mark to the left hand 21cm score line.

Mark the centre of the card along the top edge and draw a diagonal line from this point to the left hand 7cm pencil mark. Draw another diagonal from the centre to the right hand 7cm pencil mark. Cut along these lines to create a triangle at the top of the card.

Mountain fold along one diagonal line then unfold. Mountain fold the other diagonal line and unfold.

Valley fold the middle and bottom horizontal lines and unfold.

Place your thumbs and forefingers either side of the lower diagonal lines and your middle fingers underneath the diagonal lines on the back of the card. Gently pinch your forefingers and thumbs together to mountain fold the diagonal lines. The top of the card will naturally spring up. As it does remove your forefingers and fold along the lower horizontal line to form the basic card blank.

Squeeze the folds to hold them in place - the card will naturally stand up on its own.
Apply double sided tape just below the lower diagonal lines then stick to the rectangular base to fix the lower triangle to the base section as shown.