Giving any kind of notice about layoffs while expecting employees to continue working is just bad for everyone.

The employees stress out about whether they're going to be impacted. Nobody gets much work done as they update their resumes and prepare for the worst. The best people start looking for other opportunities and find them. If specific employees are told they're going to be laid off, some seek revenge.

Much better to immediately notify those impacted, revoke their access, give them generous severance instead of expecting them to work, and let everyone else know they're safe.