First I say, "Student A, place 3 pink pom poms into the tray." (the first time we do this, I give them a specific number and color that way I can glance around the room and see if everyone is doing it correctly)
Then I ask Student B to place MORE yellow pom poms into the tray than the pink pom poms.
I ask them to empty the tray and we try another one. I ask student B to place 5 purple pom poms into the tray.
Then I ask Student A to place less yellow pom poms into the tray than purple pom poms.
Another great way to use the trays is to practice patterns. I use this as a center, where the students pair up, one does a pattern on once side of the tray, and their partner needs to copy their pattern and then they switch. Here are some examples...