I saw one of these about a year ago somewhere and decided to have a go at making one too. The one I saw was made with fabric paper (like the Love Elsie stuff). I have made two using that, one is the loving couple above, but I find it to be really thick and quite difficult to work with. So instead I decided to use some fabric (pink stripes) I had and apply fusible webbing (I think they call it wonder under in the US). It worked even better than the fabric paper.
These little post it note holders are great for popping in your bag, as because they are made of fabric they don't get all dog-eared bumping around at the bottom of your bag.
This is what they look like inside.