Different departments need to make sure their users have the same base access for their respective departments. How should this be implemented?

A Sharing Set is a feature used in Experience Cloud (Community) orgs to grant portal users access to records related to their account or contact - it does not define base system permissions.

A Profile sets the baseline permissions and access for every user assigned to it, including object-level access (read, create, edit, delete), field-level security, app visibility, and system settings. Assigning all users in a department to the same Profile ensures a consistent base access level - additional permissions can be layered on top via Permission Sets.

A Permission Set grants additional permissions on top of what a Profile already provides - it is additive and not designed to define the baseline access that all department members share.

A Role controls record-level visibility through the role hierarchy (who can see whose records) but does not define object permissions, field access, or system settings.