The traditional starter railroad is on a 4x8 sheet of plywood. However, a rectangle has limitations - it is difficult to use the corner space in a practical way. Here's an easy improvement on the good old 4x8. Cut two triangles, A, and B, off one end. Flip them around and attach to the other end. Now your 4x8 is 4x10, with a shape better suited to a big oval, with a longer mainline run. Formerly wasted corner space is gone.