You will need some almond flour. If you can’t buy it, you can make your own, just make sure the almonds are really dry. Separate the eggs at least 1 hour before using or preferably the day before. And if you want to ensure all the macarons are the same size draw circles of the desired size on the back of the parchment. And do use a scale, it makes a huge difference here. And, oh yeah, don’t make them on a rainy day! (The pictures below were taken on a rainy day which is why the macarons didn't rise as evenly as they would otherwise.)
4. Fit a piping bag with a 3/8-inch (1 cm) round tip. Pipe the batter onto the baking sheets in circles about 1 inch in diameter.
Let the macarons dry about 20 minutes (a little longer is OK if you need to cook them in two batches) so a little skin forms on the outside.