Preheat your oven to 375°F (190°C) and line baking sheets with parchment paper. In a medium bowl, whisk together the flour, baking soda, and salt.

In a large bowl, cream together the softened butter and granulated sugar until light and fluffy.

Beat in the eggs one at a time, then stir in the vanilla extract until well combined.

Gradually add the dry ingredient mixture to the wet ingredients, mixing until just combined and a soft dough forms; do not overmix.

Divide the dough in half. On a lightly floured surface, roll out one half of the dough to about 1/4-inch thickness and use Halloween-themed cookie cutters to cut out shapes.

Carefully transfer the cut-out cookies to the prepared baking sheets and bake for 8-10 minutes, or until the edges are lightly golden. Let them cool on the baking sheets for a few minutes before transferring to a wire rack to cool completely.

In a large bowl, combine the sifted powdered sugar and meringue powder. Gradually add 3/4 cup warm water, mixing on low speed until smooth, adding more water if needed until it reaches a flood consistency.

Divide the royal icing into separate bowls and tint with desired food colorings (orange, black, purple, green).

Once the cookies are completely cool, use the colored royal icing to decorate them in various Halloween designs and allow the icing to set completely before storing.