The basic recipe and process I use is simple for any shape. Twice the sugar to egg whites is the ratio. So an extra large egg white in the US is about 40g (large is about 30g) so if you use three at 120g you will want 240g of caster sugar. Caster sugar is also sold as superfine sugar. If you can't find it, just give your granulated sugar a few good pulses in a food processor. It is NOT the same thing as powdered sugar.
150 grams egg whites (room temp)
300 grams caster sugar (double by weight to egg whites)
1/4 tsp cream of tartar
Pinch of salt
You will need parchment paper and sheet pans (I double mine so the meringues don't brown on the bottom)
You will be making a heated sugar French meringue.
Pre-heat the oven to 400F. Put the sugar on a parchment lined sheet pan. You will put the sugar in the oven for 5 minutes to heat it up. Meanwhile, put your egg whites in the bowl of a stand mixer with the whisk attachment. Add the pinch of salt and creme of tartar and start whipping on medium. When the sugar is heated, and egg whites have become fluffy, slowly stream in the sugar. You can pick up the parchment and use that or just slowly spoon it in (remember it will be hot). Then turn the oven off. You will be baking them at a much lower temperature (200-215F).
Continue whipping the meringue until it holds stiff peaks 5-10 minutes. Feel a small bit of meringue between your fingers and make sure the sugar has dissolved, or keep mixing for another few minutes. At this point you can fold in extracts/flavors and gel colors if desired. Pipe or spoon onto a parchment lined sheet pan. You can top them with sprinkles or colored sugar if desired, even chopped nuts. Be creative and you can split the meringue into several bowls to make a variety of different meringue flavors and shapes using one batch.
Warm the oven to 215F. *If the oven is too hot your meringues will crack so it is important for the oven to cool between the hot sugar portion and baking part of the process.*
Bake for 30 minutes and then turn the oven down to 200F. Do not open the oven. Continue baking for another 60-90 minutes. You can check the meringue by tapping one on the bottom to see if it sounds hollow, or crack one open to see if it has reached your desired doneness. The size of your meringues will dictate the length of time they will take to finish. Turn the oven off. Allow to cool slowly in the oven the sheet pans. Store in an air tight container.