1. Using a pencil, ruler and handsaw, cut the ½" x 4" wood into one 12" length for the base, and two 4½" lengths for the ends. Then cut the lath into four 12½" strips.
2. Sand all the pieces, paying particular attention to the edges and corners. 

B: Constructing the box

1. Drill two holes in each of the end pieces, 3/4" up from the bottom and 3/8" in from each side. Nail the ends to the base, nailing one end on at a time. The end pieces should protrude below the base piece to form the legs of the window box.
2. Position a strip of lath on each side of the box, level with the tops of the ends. Drill a hole at each end of the strips, and then hammer in the nails to attach the strips to the end pieces.
3. Repeat step 2 to nail the other strips below the first strips, leaving a gap of about 5/8" between them.

C: Finishing

1. Sand the window box all over with the medium grade sand paper.
2. Seal with two coats of clear varnish or with paint in your chosen color.

D: Filling the Window Box

1. Look for small plant pots that will fit into the window box. You should be able to fit three or four in. Make sure that the pots have saucers and that these will also frit into the box. Put a few small pebbles in the bottoms of the pots to assist in drainage, and fill the pots with soil. If you are using good quality potting mix, you will not need to add the pebbles. 
2. Plant the pots with seeds from dwarf varieties of herbs or flowers. For best results, use plants that require similar growth conditions.