Essentially, all you have to do is to cut a portion of the large design so that you can slide your photos, embellishments or other papers underneath a section of the patterned paper.I adore my Westcott Craft knife because of the soft grip and light weight.The key to doing this technique well is to leave portion of the paper attached. Don't cut the design completely out. Cut small sections first, enlarging the slit just a bit as you go so that the papers or photos can slide under the slit with ease. You don't want to force anything in as the paper might buckle and become lumpy or bent.
Sometimes a photo just can't do a technique justice. Take a look at this video in which I explain the technique in further detail.