Based on ingredients available to make Royal Icing you can use
Liquid Egg Whites
Fresh Eggs ( raw or in-shell pasteurized)
In a bowl of your mixer whisk together water, meringue powder and cream of tartar. Add powdered sugar and mix on low speed with a paddle attachment. Mix till thick. It can take up to 10 minutes. Beat in extracts.
Whisk together liquid egg whites and cream of tartar. On lows speed, gradually beat in powdered sugar. Mix for several minutes, mixture will gradually thicken and become glossy. Beat till thick then add extracts. It should take about 7 minutes or so.
Separate egg yolks from egg whites. In a bowl of a stand mixer beat together egg whites, cream of tartar and gradually keep beating in powdered sugar. Mix on low speed till thick. Then beat in extract and continue mixing until thoroughly mixed in. Icing should be thick and glossy.
Make sure your tools are grease free. Wipe them dry with vinegar.
I generally use stand mixer to make royal icing. If using 1/2 pound batch(4.5 cups powdered sugar) you can also utilize a hand held mixer. Be sure to add powdered sugar gradually.
Once Royal Icing is prepared it can be colored, thinned down to more fluid consistency for cookie decorating. You can then fill your piping bags and decorate as desired.
If you plan on using royal icing later be sure store in an airtight container covered tightly with a plastic wrap to prevent crusting.