Think of the "sketch" as being a formula or layout suggestion, not an actual sketch of something. This term really threw me at first until I actually saw one of the original layout sketches. I thought that people would be actually sketching freehand on cards, LOL!!
AndreaSophia (I hope I got that right!) draws a "sketch" of the basic layout or formula that would be nice for the challenge takers to include in their card. You then interpret it anyway you so desire, as you can see by all the fabulous cards being generated by this talented group of women! This is sort of like the first few pages of the old SU! Stampin' Memories catalogs in which they gave a few scrapbook page layout examples. Clear as mud? HTH!!!