I am in love with Pear Deck (https://app.peardeck.com)! If you are looking for a great way to conduct common formative assessments within your class lecture or presentation, consider using Pear Deck. Pear Deck is free and is used as an add-on to your Google Slides.
If you are like me, I'm still using PowerPoint. But, it is so easy to convert your already made PowerPoint slides to Google slides. Next, Google Pear Deck and sign up for your free account. While in Google Slides you can easily make slides that become interactive for kids and it also allows you to drop in quick common formative assessment slides to make sure your kiddos are learning. It is an amazing tool and a must use.
Even if you do not have technology in your classroom, it can be used with the whole group. If you do have 1 to 1 computers or just a few, it works well. Check it out!