I have seen this look quite a bit and did a little research to make sure I knew how to achieve it. For August, my stamp clubs got treated to this technique and some water-coloring too for these cards.
I let my club members choose their designer paper from the 3 sheets I picked out to coordinate, and we also made a page in our Technique Book for this technique.
We used the Farmers Market designer series paper and Market Fresh stamp set that coordinates from the annual catalog (the big one).
Tip: Put dimensionals all around under the frame for a deeper inset look. I used 6 dimensionals on each card.