Those few seconds of "blank time" before opening the textbook are the most tedious part, right? I make it a habit to toss out the next task the moment 90% of them have it open—like, "Those who’ve opened it, read today’s objectives three times!" The trick might be creating a state where everyone is "preparing" rather than just "waiting."
In such cases, you end up getting 90% of the kids to participate first by saying something like, "Number 3 on the square. 'Taro-kun went to the flower shop. 〜〜 (details omitted below)' Read up to here. San, yes."
At first glance, it looks like you're leaving the remaining 10% of the kids behind. →