We keep our bags of coal in the front deck under the cratch cover, stacked up side by side at the front where they don't interfere with getting on and off the boat
We have a coal scuttle which is kept beside the fire and we fill it using tongs till the bag can easily be lifted and the coal tipped onto the scuttle. No mess or coal dust on the front deck
I think the previous owners of the boat had a big plastic box on the front deck and the coal was emptied into it
We felt that a box would reduce the available space so didn't go down that route