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@RebeccaBoyd we sometimes keep the shells on the counter in metal. But like you we have only a few hens so we didn't need a big metal bowl.
We put the air-dried broken shells on a smaller metal pie or cake tin inside the oven. We mash up the shells so they fit nice in the tin. We remove the tin from the oven whenever we bake something.
After we bake we turn off the oven & put the egg tin back in the oven to heatup the shells (it's said the heat kills any bacteria). We take the tin out of the oven when cool & use our old Magic Bullet blender &
grind the treated shells down to a very fine powder ~ then store the powder in a container. When we fill up the container we store the powder away in a garden box to use the following year as an added fertilizer mulch in the raised garden beds.
We don't feed egg shells directly back to the chickens since they use oyster shell. But the following garden season when harvest is over & the hens dig thru the mulch I'm sure they find some shell powder. Sometimes I don't have time to Magic Bullet grind the shells out of the oven so we toss the treated shell pieces into a baggie to accumulate till I have enough to grind up a batch but only heat treated go into a closed baggie or closed container.
Coarsely hand-crushed egg shells sprinkled around vegetable or flower plants deter snails & slugs who don't like to crawl over the sharp edges of egg shells but I personally don't do it cuz of the aesthetics. (I use Sluggo against snails/slugs which is pet safe).
Amazon.com : Monterey LG6515 Sluggo Snail Bait
Magic Bullet blender/grinder