view options - pin one user, spotlight speaker

I do a monthly Zoom where the focus is on a 99 year old class advisor "Les". He's mentally very sharp but not a techie and his vision is failing. There are often 40+ people on the Zoom. When someone speaks, Les has a hard time identifying who is talking as he scans the multiple screens to find the talker. As a result, he misses the beginning of the conversation.

What's the best way to have the current speaker's video prominently on-screen so Les doesn't have to look through multiple pages of participants? Ideally, Les' video would always be on-screen but its ok if that's not easy.

Thanks,