The first thing to research is how mask based icons work in general. There's a dearth of good information, but I did find the Icons Special Features section of the ADW Theming Guide to be useful. Alternatively, you can follow along and examine my images to gain an understanding of what I've done.
I began with mathur's Icon-Pack Template, but I've modified it to fit my needs by removing unnecessary bits and the parts relating to non-mask based icon packs. See the attached example, Crinkle.zip
Once you've downloaded Crinkle.zip and imported the code into eclipse, there are several things you'll need to alter:
First, you must rename the package. This can be done by doing one (or both) these actions:
[project (context menu)] > Android Tools > Rename Application Package
[package (context menu)] > Refactor > Rename
Second, ensure the correct scale factor. This can be found in two places:
assets / appfilter.xml
res / xml / appfilter.xml
Third, make sure your informational strings are correct. There are two locations:
res / values / strings.xml
res / values / theme_config.xml
Fourth, and most important, add your own icons. These can be found in res / drawable-xhdpi, and they are:
icon.png - the application icon
iconback.png - the background image
iconmask.png - the transparency / opacity mask
iconupon.png - the overlay image
Now test it out.
My finished icon pack is live on Google Play under the title Crinkle Icon Theme.