Create Signup groups in LEO to allow students to choose their own groups - as with group-based assignments, for example.
As a lecturer, if you decide to use signup groups, first determine how many students you will allow per group and therefore how many groups will be needed.
In the LEO unit, select Administration menu > Unit administration > Users > Groups.
Select the 'Signup groups' tab.
Click the 'Create signup group' button.
Give the group a name, e.g. "Signup group 1", type in the 'maximum number of members' and click 'Save changes'
Repeat steps 3 and 4 until you have the required number of groups.
When students enter the LEO unit, they will be able to go to the Navigation menu > Current unit > [Unit name] > Participants > Signup groups. You could choose to promote this link as a URL in the list of activities in a section.
The student can select a group to join. They can also see which members a group has before joining.
If a particular signup group has reached its maximum number of members, the student will have to select a different group.