Here's my card. The background and the design in the circle were stamped using Circle Circus. Colors are Tempting Turquoise and the retiring In Color, Lucky Limeade.
The rounded corners have a bigger circumference than those done with the corner rounder punch.
I used one of my circle punches (I can't remember which - either 1 1/4"
or 1 3/8"). Basically, go in from the top (as opposed to from the
bottom, which would just punch out a whole circle) and stick the corner
of the card in the punch as far as it will go.
I stamped the inside of the card, too.
Now that you've seen my card, head on over to the TSSC blog to see the other design team samples and to link your own take on the sketch.