·Tub [or large bowl or other container]
·Bag of oatmeal [or corn meal, lentils, or other grains]
·Small trinkets found in the bottom of the toy box [I raided his recently acquired treasure chest]
I had a bag of old random grains that I have used for an indoor sandbox on a rainy day [incidentally, also on a day that I was going to vacuum anyway].
After hiding the wee treasures in the grains, we used different tools to dig out the goods.
Spud developed a pretty intricate system that involved another bowl in which he could carefully pour the grains.
He also had some less than conventional techniques.
It all worked.
It was also nice to have a special place to put the booty.