So far, I’ve made two for them, both with three layers. I include things like matchbox cars, shark’s teeth, shells, clothes pins, dice, buttons, some little plastic animals, and a few other random things.
I take a bowl, put about 1/3 of the items I have selected into it and fill the bowl about 1/3 of the way with water. Then I stick it in the freezer until that part is frozen solid. Then I repeat the process 2 more times until the bowl is filled with all the items and the water is almost up to the top. Then I let it freeze until completely solid. Freezing it in stages ensures there are fun items to find all the way through the ice block instead of only at the bottom.
When the ice blocks are ready (it does take awhile, so plan to make it a day in advance), I hold the bottom of the bowl under running water until the ice block pops out. Then I put it on a cookie sheet on the screened porch or outside and give the kids some tools to use to help melt the ice: toothbrushes, a medicine dropper, a turkey baster, a bowl of warm water, and some rock salt.
They played with it for a good amount of time both times!
I always give them a little bowl to collect their treasures in as they de-ice them:
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