To start off, grab your drill and detach the top cushion from the hinges. Measure the cushion; your tabletop needs to be the same size as the cushion. Because of the ¼" lattice, we reduced the width of the plywood by half an inch. You can do the same on the ends, but it's not as necessary as on the sides where it will interfere with the hinges.
Lightly sand over the legs to give texture for the paint to stick to. Lay out your drop cloth and following the directions on the can start spray painting.
*Note: It's really difficult to spray paint outside when it's windy!
Next, leave the paint to dry and start cutting lattice. Measure all four sides of the plywood, and cut the lattice strip accordingly at a 45° angle. If the lattice is a hair longer than it should be it will bend when you nail it and everything will fit together tightly, whereas if you cut it a hair too short there will be a crack that nothing will be able to fix. So if you're going to err on a side, err on the side of being too long.
Now for staining! Because of the different qualities of birch and hemlock, we stained the lattice only once while we stained the plywood with two coats. This ended with almost the exact same shade on both types of wood. Yay!
After the stain has been wiped down and dried, line up the lattice along the edge of the plywood. The bottom edge should be flush with the plywood so as not to interfere with the hinges. Hammer in a nail on either side of the lattice and then work your way in nailing every few inches to secure it fully to the plywood.
At this point the spray paint should be dry enough to attach the top to it, but that will depend on how many coats you applied and the kind of spray paint you used.
Because we didn't have the original cushion with us we did this part a little differently. Here's the way I would recommend that you do it: On the original cushion measure in from the ends to where the holes for the hinges are. Measure in the same distance on the plywood (taking the lattice into account) and draw a vertical line. Now unscrew the hinges from the bottom of the bench and line them up along the edge of the tabletop with the outside hole over the line that you drew. Mark the holes and pre-drill them. You can attach a piece of tape to the drill to ensure you don't go too deep. Screw the hinges first into the tabletop, and then into the bottom section.
There should be a metal arm that slides back and forth and keeps the top up when you open it. Measure where this attached on the old cushion, and then mark holes for it on the new tabletop. Pre-drill the holes and then put in the screws.
Last step: applying the polyurethane sealer. This will help protect your table from spills and will give it a nice sheen. Follow the directions on the can, and make sure that you wait until the stain is fully dry before applying the sealer. Once the sealer dries you are ready to enjoy your new side table!