In the beginning I do only a few slides at a time and I always engage with the students through each slide. There are many math talks that start with the slides. We discuss things such as, "How can you count this quickly?" "What would this look like as an equation?" "How many more do I need to make 10?" "Could you count this more efficiently by grouping them and/or counting by 2's, 5's, or 10's?"
Before I flash a new slide, I remind the students my #1 rule. Stop and think. Then when I say, "Release", they are allowed to yell out the answer. They must think, keep the answer in their heads, then share out. This gives my slower/lower students time to think before all the noise and commotion of answers being shouted out. Hope you can use this as much as I have. My kids LOVE this activity.