Have students watching the presentation use the same rubric you do and grade the presentations. (We do this, and I don’t think it offers much after the first few times. I like that it makes students think about what will go into their own presentations, but they tend to be generous graders.)
Have all students write down something they liked and something they thought could be improved on.
“Randomly* call on two students after each presentation – one to give a constructive criticism, and one to give a compliment. The potential of being put on the spot should keep most students paying attention.”
Students write one thoughtful question they would like to ask. Then, the presenting student(s) chooses one classmate to ask their question and then the presenter responds to it.
“A TAG sheet has three rows: Tell them something you liked. Ask them something that was unclear. Give advice for next time. These seem to work well IF I say that they must offer three pieces of advice, not necessarily one T one A and one G.”
Finally, this article had some interesting ideas: https://www.chronicle.com/article/Doubling-Down-on-Student/234622
This in particular: Have students do a longer presentation – then write down what they thought went well, what didn’t and what they’d want to change. Students can turn that reflection of their own work in for credit.
One site suggests having them present to just 1 other person (or if working in groups, have 1 group present to another group), and have 3 or 4 presentations happening at a time.
You could even have them do this on consecutive sessions, so it’s a shorter time for any 1 class. Then swap groups presenting next class.
And then have students do a shorter presentation implementing those changes later in the term. (Shorter, because they have to sharpen their message, hone their skills, etc.)
In one bigger class, students also get to vote for their favorite presentation in their smaller discussion sections. The element of competition is an fun incentive for some. The professor had mugs made up, but a trophy from Goodwill with WINNER in sharpie would be tempting.
*random is hard (have a system – you can use an app, or put all student names in a hat/on index cards/on popsicle sticks to help.) Give them points for asking.