Tell people in the right order.
Leaders first, managers second, everyone third, within a short window. Managers should never hear news second-hand.
State the reason before the detail.
Use the right voices.
The leader explains why. Managers explain what it means locally. Peers explain how it works. Each voice answers a different worry.
Keep going after the announcement.
People remember how change was handled. Plan regular updates, a place for questions and a date for answers.
Close the loop: say what changed because of employee input.