Having coal clamps which produce 40+ coal is great but when you want to mass produce metal with the continual flow of coal and without the needs to expand claim/build more boxes or chests [that will litter your base anyway], leaving coal piles where they are is a problem. So, I suggest coal bags to store 60 of those precious black lumps. It can be made from 4 cotton cloths (I prefer hemp cloth but that's out of the question, obviously) and coal bags once filled are liftable objects which then can be put on sled or stored in shed. This brings me to shed. If it could have about 5 slots in addition to current space to store object, such as sleds, boulders, coal bags, etc... it would be great help.
P/s: There is another thread that vaguely mentions about this idea and it has other suggestions so I make this separate topic to further discuss the idea.