I love one sheet wonder cards - they are great when you want to make a set of matching cards in different designs but fundamentally using the same pattern. You take one sheet of A4 I used Stampin Up Whisper white and you stamp over the whole thing using a stamp set .. or two of your choice you then have some great patterned paper that you can make several cards from.
I used the Stampin Up colours Not Quite Navy for my card base - its a standard A2 card. I then used matching not quite navy ink, sahara sand for the leaves which really adds some subtle interest and is such a fab colour, poppy parade now sadly retired and daffodil delight.
Here's a close up of my main stamped panel.