I used a cottage cheese container and decorated it with some colorful 'duck tape' that I found at Michael's the other day, and was excited to find a use for. I used sliceez cutter to cut the holes, but I think any kind of Exact-o knife, or scissors would work fine too. I used a penny to trace the circles for the holes - they are slightly smaller than the larger of the two sizes of pom pom balls are.
I happened to have a half bag of leftover pom pom balls from some crafting Clara and I had done for my Dad's room when he was in the care home. They weren't the best things for that kind of crafting at her age anyway, so I was excited to find another use for them - especially since she likes to just play with them as they are anyway.
Clara didn't really pick up on this right away, but the little girl I babysit for absolutely loved it. She poked all of the pom poms through the holes and then asked me to dump them out again for her - about thirty times, I think. Clara became interested then, but only because her friend was, I think. I might have to make another one for tomorrow so they don't fight!