It is made a slight bit different to how I thought, and have just spent ages trying to work out the folds. only to give up and cheat.
You score your card at the half way mark. to make a normal card mark the edge.Call this Dot A
Mark the centre of the card front Call this Dot B
Mark 1/8" from the B. .Call this dot C.
Mark 1/8" from A. Call this dot D..
From the corner of your card measure uptowards A. only 1" call this E.
Score from A to B. This is the central envelope shape.
Score from C to D.
You need to score from D to B.
Score from E to C.
Repeat on the other side.
It should fold to cheat the card.
You can make E larger than 1" as it is the little flap at each side.