I have seen this done on a few blogs with various dies (not just nesties) and really liked it, its great for scraps of card too and you can make them what ever size you desire!
Mine is made using the Lables 8 die set which is my fave set right now! I used the biggest one for the card and the size down for the background, the beauty is you know its all going to fit together wonderfully!
all you need to do is cut 2 of your chape from card, take one of the shapes and score about a cm all along one edge (this shape will be the back of your card) then stick the 2 shapes together so that your scored shape is at the back and the scoreline is on the left hand side, the pic below was of the back of my card which was landscape but the same idea applies!!
Then you can decorate the front of the card anyway you like but i have used a matching shape to create a bit of a border
This is a mega simple (and quite cheap!!) card to make, i used some K & Co patterned paper and tsome ribbon and just popped gems and pearls around the design to give it some bling! A great any-occasion card!
You could do this with any die cut shape really, it would work well with circles and flower shapes too and even the smaller nesties as dinky tags!