[reflexe]

From my experience (as a team lead who had to do that a few times unfortunately):

First, each department is usually allocated a number of employees they should layoff (based on high management priority).

Then, each department has to decide how to allocate it internally (cut-off teams entirely, or layoff a number of employees per team).

Then it goes to mid level management and lower management which has to choose specific employees (based on a number of criterias but usually based on performance).