Cut your cardstock to 7 1/2 x 5 1/2, and then score at 3 1/4.
Fold at the score line. Score again three times just to the right of the opening edge. I just found a groove that would work, and then moved my card over a little for the remaining two score lines. Do not fold on these lines. They help with flexibility when opening and closing the latch.
Decorate your front focal panel and choose what you will use for your latch. It can be a die cut shape, or a plain sentiment square, or any number of things. I chose a simple layered circle and flower.
Assemble your card, using foam tape for the latch, just to the right of the three scored lines.
I used a watercolor wash for the background, and then stamped my images on top. Since it's also watercolor paper, the images are not as crisp as they would be on smooth cardstock, but I liked that effect. The Tower is stamped twice and popped up with foam tape. I used the wrong stamp for my "postage cancellation," (the rectangle instead of the circle) but decided to just leave it!
And the finished product: