Raise bin off the surface so that air can circulate underneath. This type of bin will need a tray to catch any liquid that goes through the bottom. An old wooden box or drawer will work as a worm bin. However, wooden bins, because they are always wet, might last only two or three years. Do not use treated wood to build your bin.
Treated wood can contain arsenic and other chemicals used as preservatives.
A hinged lid is preferred but a piece of burlap or black plastic can be used as a lid to keep the light out and moisture in.