I used fairly blank cards to begin with and then just cut scraps and placed them on the card, sewing them down with about 1/8 in seam allowance. This is very similar to tickertape, a technique I absolutely LOVE doing.
When picking fabrics, I tried to pick ones that were more graphic and/or allowed me to fussy cut to give more interest to the individual pieces. I was able to do 4 cards in less than an hour, pretty quick I would say for something that gives a much more personal touch than a pre-made card.
I definitely see much more of these in my future. Great use of scraps and fun to make and quick to complete on a day you need an easy finish or don't have enough time to make some progress on another project.