I usually cut a piece of paper the size of the block where I want the design. In your case, I would do the 16-patch and another paper with the sashing 4-square plus the other rectangular block. Then I use a pencil to try out designs. Like Maureen NJ, I recommend Cindy Needham's websites. If you search for Cindy Needham Ultimate Stencil, you will find a Free 27 page handbook for download that has two pages of diagrams you can print which gives guide lines to help you draw. She also has videos to show how to use the diagrams.