Add a line of cheap ½" trim molding two or three inches above your baseboard molding and pain the wall between the two pieces the same color. Use a piece of wood of the desired thickness of the gap to make sure your trim molding is evenly spaced. Then, tape off the top and bottom and paint the entire new molding area.
i think this might be my next project... Faux Crown Moulding Decorative molding is hung a few inches below plain molding on the ceiling line. Then both pieces of molding and the space in between are painted the same color to make it all look like one continuous piece of crown molding.
New York Window - Fotobehang - 232 x 315 cm - Multi