Use a power miter saw or a circular saw to cut the ends of the 2 by 2 verticals and slats at a decorative angle. Using 3-inch screws, fasten the four verticals in place inside the cross braces on the side opposite the bench. Screw the eight slats on top of the beams. Screw the decorative corner braces in place. Finish the arbor with stain, or apply primer and paint.