In 3-4 additions, use a rubber spatula to gently fold the meringue into the dry ingredients. It will be thick and pasty at first. Keep folding by wiping the sides and bottom of the bowl with a rubber spatula.
After all of the meringue is added, fold until the batter flows in thick ribbons from your spatula without breaking. If you lift the batter up and draw a figure 8, it should disappear into the batter after about 10 seconds. If it doesn't disappear or if the batter breaks off of the spatula, keep folding and check again after every few turns.
Pipe the shells: Add the macaron batter to a large piping bag with a ¼-½" round piping tip. Hold the piping bag straight up and down with the tip right in the center of the circle on your template. Gently squeeze the bag until the batter spreads and almost fills the circle. Stop squeezing and lift up with a quick twisting motion.
Once you have all the shells piped, lift the pan up about 5" and drop or bang it firmly on your counter several times. You should see little air bubbles come up to the surface and pop.
Let the shells dry out on the pan for at least 30 minutes, or until they form a skin on the surface. You should be able to gently touch the tops without wet batter sticking to your finger.
Arrange your oven rack to the middle position and preheat your oven to 300°F/150°C. Bake the macarons, one baking sheet at a time, for 15 minutes each. Take them out of the oven and let cool completely before touching them or trying to remove them from the pan.