Preheat oven to 350°F. Line baking sheets with parchment paper or silpat liners. Set aside.
In a large bowl, whisk together flour, baking powder, and salt. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment, cream butter. Once smooth, add sugar and extracts. Mix on low speed until combined. Add egg and continue to mix. Scrape down bowl as needed to ensure thorough mixing.
Add flour in two additions. Continue mixing on low speed until dough comes together. Divide dough into two equal parts. Working with one piece of dough at time, place on a lightly floured work surface. Roll to a thickness of about ¼-inch. Stamp out desired cookie shapes. Gather scrapes and re-roll as necessary.
Place cookie cutouts on prepared baking sheets. Bake for 6-8 minutes until the edges of the cookies are set. Allow to cool in pan for 3-5 minutes until cookies have firmed up enough to move. Transfer to wire rack to cool completely.
In the bowl of a stand mixer, whisk together warm water and meringue powder. Let sit for 3 minutes.
Add powdered sugar in three additions. Using a paddle attachment, mix on low speed. Add vanilla extract. Mix until icing holds a ribbonlike trail on the surface of the mixture when you raise the paddle.
Divide icing into smaller bowls. Color one orange, one green, and one purple. (Notes on food gel colors used listed below)
Save any remaining royal icing by covering surface of icing with a damp paper towel.
Assembly and Floodwork:
If using piping tips, place inside piping bags (pastry bags). Partially fill piping bags with desired colors.
Start by piping a general outline using a #2 piping tip. (#0, #1, #3 also work) By the time you have outlined all your cookies, the first outline should be dry and ready for flooding.
Thin some royal icing using warm water. Add ½ teaspoon of water at a time to your royal icing until it is loose and pourable. Using a squeeze bottle, piping bag, or spoon, flood the inside of the outlines with the thinned out royal icing. The icing should naturally flow to the edges of the outline. If it needs a little help, you can use a clean toothpick to drag it outwards. Use a toothpick to also pop any air bubbles that may have formed on the surface. Let the royal icing dry at room temperature. This takes about 15-20 minutes (something more depending on the humidity of your room).
Once dry, use the piping bag used for creating the outlines to pipe additional decor on top of cookie to enhance shape and texture.
Allow to dry completely before stacking. Store at room temperature. Keeps for 3 days.
* I like to use pandan extract (clear color, not the green one) instead of almond extract. It adds a nice tropical, almost coconut flavor. You can substitute almond extract, lemon extract, or flavor of choice.I use AmeriColor soft gel food coloring to dye the royal icing:
For the orange, I used a combination electric orange, electric yellow, and a touch of super red
For the green, I used equal parts electric green and forest green