Place a sheet of 1/2-inch treated plywood on a flat surface. Tape an ornament template onto the plywood. Craft stores sell templates in a variety designs, or you can draw your own on paper or cardboard, then cut it out.
Trace the outline of the ornament shape onto the plywood with a pen or marker.
Position the plywood on the sawhorses or workbench and drill a 1/2-inch hole nearby and outside the ornament outline.
Insert the jigsaw blade through the 1/2-inch starter hole. Turn on the jigsaw and cut over to the ornament outline. Carefully cut out the ornament following the outline. Shift the plywood as needed to allow the jigsaw access to the trace lines.
Sand the cut edges, the front and back of the wood ornament with medium-grade sandpaper. Go over the same areas again with light-grade sandpaper. Remove the sanding debris.
Paint the front and cut edges of the wood yard ornament with acrylic paint or exterior latex paint. Allow the paint to dry. Paint the edges and both sides of the wooden ornament with exterior polyurethane. Allow the polyurethane to dry.
Cut a 2-inch-wide, 1-inch-thick strip from treated wood to fit the height of the ornament, plus 12 inches. Paint the front of the strip to match the front of the ornament. Let the finish dry. Cover all sides of the wood strip with exterior polyurethane. Let the polyurethane dry.
Attach the wood strip to the back side of the wooden ornament with decking screws. The extra 12 inches should extend from the bottom of the wooden yard ornament.
Insert the 12 inches of the wood strip into the yard to stake the ornament.