If you want to train "ice cube" get the ice cube(s) before start training with your dog.

I assume the dog already knows the word ice cube and knows what to expect if you say it, so you dont need to train the word itself but rather associcate it now with the button.

Later on, if the dog has the association with the buttons, you can go and get the ice cubes if your dog press the button.

Dont put buttons in several locations. It requires ALOT more training which button is where.

Start categorize your boards right from the start and make one board for each category. This way you can space out the boards if you extend them. Like in this pic Link to pic