Thanks to some encouragement from friends on Facebook I decided to try again with an envelope template. The ones I bought are great but the design wastes a lot of paper and needs a fairly large piece so that most of the cute illustrated books I find are too small. When I realized I had an envelope that was just what I wanted I pulled out a ruler, Xacto knife and the cutting mat and set to work. The result is much nicer than my first freehand attempt.
I may have gotten a bit carried away with envelope making.