The most fundamental step to protect sensitive data in Salesforce is to set the most restrictive access level at the organization-wide default (OWD) level. For sensitive HR data managed through the Case object, setting the OWD to 'Private' is the correct initial action. This configuration ensures that, by default, a case record is only accessible to its owner and users explicitly granted access through sharing rules. This application of the principle of least privilege is the cornerstone of securing confidential employee information within the Employee Experience Management solution.

A. Disable all approval processes on the Case object: Approval processes are for business logic and workflow automation; they do not control the fundamental visibility of records.

B. Disable the Grant Access Using Hierarchies setting on the Case object: While this is a crucial secondary step for HR confidentiality, it is only effective after the OWD is set to Private. It is not the foundational configuration.

C. Mirror the Org Chart into The Role Hierarchy: This can be detrimental to security, as the role hierarchy controls data access. A manager's position in the org chart should not automatically grant them access to a subordinate's sensitive HR cases.

1. Salesforce Help, Organization-Wide Sharing Defaults: "Of all the record access features, organization-wide defaults have the biggest impact... Setting an object to Private makes those records visible only to record owners and users above them in the role hierarchy." This establishes the OWD as the foundational security setting.

2. Salesforce Public Sector Solutions Documentation, Set Up Employee Concierge: In the "Configure Sharing Settings for Employee Concierge" section, the first instruction is: "From Setup, in the Quick Find box, enter Sharing Settings, and then select Sharing Settings. Click Edit. For the Case object, select Private." This directly confirms the required configuration for the Employee Experience solution.

3. Salesforce Architect's Handbook, Record-Level Security: The data security model is layered, with Organization-Wide Defaults being the first layer of control that is evaluated. "OWDs are the default access level that a user has to records they do not own... This is the starting point of your security model." This confirms that OWD is the primary and most critical configuration for establishing data protection.