Hello Richard, welcome to the forum Here is a link to a thread on this site that has many photos of coal bins:
Because every house, basement, garage, yard etc is different, virtually every coal bin will be different. Here are some general cautions and idea:
A ton of coal is about 40 cubic fee
Put a solid waterproof floor in the bin. The coal often comes wet, and you don't want the floor rotting or getting muddy.
The solid floor is so you can shovel off the floor without picking up dirt, mud, gravel, wood splinters etc.
Brace the sides to be strong enough to not swell or bow out from the coal pushing from the inside. Coal is pretty slippery, and constantly exerts a lot of force on side walls.
Make some kind of variable height doorway so you can fill the bin, [doorway top high] and still access the coal and floor of the bin as the coal is used [doorway low]. A frequently used idea is to make the doorway a vertical slot filled with sections of 2x6 or 2x10. Just remove each board as the coal level drops to provide easy access to the coal.
Materials can be plywood with 2x4 and 4x4 bracing, pressure treated plywood is best for the bottom, or concrete block on a concrete floor, and any combination of standard building materials
If you put the coal bin outside, make sure you have a roof or cover on it to keep the rain/snow off the coal, it will freeze into a solid lump and be very difficult to get out of the bin.
Hope this helps, take a look at the above link.