The deployment process needs to detect whether a bucket already exists and, if not, create it. Guise Mummy should also be able to automatically configure the bucket for web site hosting — there's no point in requiring it to be done manually.
A new "phase" should be added (i.e. the deployer API should be expanded) that equates to prepare-deploy, and that's where the bucket creation and setup would be done. This should be checked on each deployment. (In the future a command-line flag or other configuration can be added for skipPrepareDeploy. Analogous to Maven, this should probably be added as part of the entire life cycle after more thought.)