Work with classroom teachers, who spend all day with their students, to create strong heterogeneous groups. Since station work includes writing, reading, speaking, and listening, it is important to mix students that have various strengths. Along with the mix of academic strengths, you also want to consider social-emotional strengths. A group made completely of outwardly strong leaders can be as much of a disaster as one with all students that struggle with the target language.
I created a Google presentation with the groups so that it was easy to get them up for the class every day. The groups are assigned to a symbol or color that rotates each day. As a result, the groups don’t need to change, just the basket they find and the leader.