There are lots of ways to convert a 12x12 page sketch into the basis of your card design. One way is to simply scale everything down, perhaps leave out or combine a few elements, and adjust to make them fit the size and shape of card you are creating. Another way is to think of "cropping" the layout sketch so that you are only using a portion of it. Or, maybe you just take some inspiration from one or two of the major elements of the sketch, and go from there.
Here are some examples. By pure coincidence, Dana and Morag both used the same sketch as their card inspiration, this one:
Dana's cute card is a mostly literal, scaled-down interpretation of the sketch, with the sentiment in place of the photo, and the stars from the sketch reflected in the card design, but used in a different way (a single star in the middle of the layer of embellishments).
Morag's adorable little bear card incorporates the focal point photo and the circle elements of the sketch in a slightly different arrangment. She replaced the stars with buttons and added a ribbon, and put her sentiment in place of the title in the sketch.
For my card, I used this sketch:
I basically incorporated the paper placement from the sketch, simply scaling everything down to fit my card. I put my sentiment in place of the photo, and left out a few elements so as not to "crowd" the card design. I loved the little corner embellishment on the sketch, so mimicked it with a stamp that runs off the corner of the card.
I would love to see your sketch-inspired cards! You can check out the Allyscraps Sketch Archive Thread for my past sketches, or use any layout sketch from your favorite sketch site!