My reputation for bizarre knitting being what it is, I've been asked by both North Georgia Knitting Guild and Atlanta Knitting Guild to teach a little bit about how to double knit. For NGKG, I'll be teaching a mini-workshop at our Beat the Heat Retreat on Saturday 21 July. AKG was planning on having a program on double-knitting later in the summer, and originally it was going to be during a month when I couldn't attend. But that changed. So on Thursday night, I'll be presenting a program on double-knitting to AKG. This works out fine, as I got my act together and knocked out the project and handout for NGKG.
The project requires casting on (Judy's Magic Cast-on preferred), working in double-knitting, grafting hem closed (to make casing), and cords. There are a bunch of different ways to make the cords. You could even make the soap sack as a workshop, and then make kumihimo cords as a second workshop.
By the way, I'm purposefully not showing you the plain white side. I experimented with combination knitting on this. Interestingly, my purls ended up my tighter than my knits, so that I got very significant rowing out, and it was much more pronounced on the plain side. The plain yarn also seemed to be every so slightly thicker, so perhaps that contributed to the problem.
If you'd like to try this pattern yourself, you can download it from Ravelry.