In the end of the howto there's a list of tools. The packagae for 'sandboxme' is app-shells/sandboxshell, not app-shells/sandboxme.
Created attachment 19813 [details, diff] Patch to s/sandboxme/sandboxshell/ Thanks for reporting. The following patch should solve this issue. If a docdev can review this one I can commit.
Ah; the new doc-policy is up so no review is needed anymore for such small fixes :) Committed.