.75 cubic feet is only 1/64 of a rick of wood. It will be a very small box. It needs to be at least 18 in long for a stick of wood to fit, and oh yea, firewood varies in diameter because trees vary in diameter and shape. A rick of wood is 48 cubic feet- 4' x 8' x 18" (1.5'). I'd say just keep workin on it til you build one you're happy with.
