As in — there are 10 activities on the Common App. On the essay, should I elaborate on a different activity than the 10 activities on the Common App? (So it’s not redundant and I can say more about myself.) Or should I elaborate on one of the 10 activities in the common app?
I’d do a slice of life essay focusing on one of the activities you already listed. If you already have ten listed, adding another risks making you look like a “jack of all trades” type. The slice of life should focus on one moment or one experience in one club. The idea is to discuss your impressions or how you reacted to that moment, not to go into depth about the club’s objectives and activities.
You could also write about WHY you like/were drawn to a particular activity.
For example, my son was president of his school’s investment club. Nice, but there are thousands of presidents of investment clubs; by itself it is run of the mill. But my son wrote that he was drawn to the investment club because he was a news junkie and read the BBC, Al Jazeera, and NY Times websites every day, and was extremely interested in how events affected the markets. The focus of his essay was really about how engaged he was with world events, which was absolutely true, and also something that didn’t show up on his transcript, or in any awards. Yet told the AO that he would be an asset to their campus. Don’t know if it made a difference, but I am pretty sure he wrote the only essay like that, out of those thousands writing about investment clubs.
My kid wrote about a volunteer activity he had organizing the neighborhood associations papers. He described a few of things he learned and about how it made him feel like a real historian as he realized what he found out, and what information was still missing. I think the essay really showed the way his mind works and how he analyzes material.