large Christmas tree or snowflake cookie cutter; small Christmas tree or snowflake cookie cutter; small star cookie cutter; 2 silicone baking mats; wooden skewer; hammer (or you can use a rolling pin); pastry bag; coupler; small star tip #30; plain tip #6
Preheat the oven to 325 degrees F. Line 2 baking sheets with silicone baking mats.
On a clean work surface, dust with flour and roll the sugar cookie dough to 1/4-inch to 1/2-inch thick.
Using your large Christmas tree or snowflake cutter, cut out shapes and place onto a prepared baking sheet. Re-roll the excess dough to repeat this process until you have used all the dough.
While on the silicone mat, use the smaller cookie cutters to cut out shapes from the centers of the cookies.
Place the hard candies into resealable plastic bags and crush using a hammer or the rolling pin until they are almost a dust; you want the pieces to be small enough to fit in your cutouts.
Sprinkle the crushed hard candy into the cutouts you made in the center of each cookie; be careful not to get any on the top of the cookie. Fill each hole two-thirds of the way.
If you are planning to use these as ornaments, make a smaller hole towards the top of the cookie using a wooden skewer.
Bake the cookies until just golden brown around the edges, 10 to 15 minutes; the candy should be melted and bubbling in the center. Allow to cool completely on the pan before attempting to move.
While cooling, place your royal icing into a pastry bag with a coupler and a decorating tip. Decorate the tops of the cookies with the royal icing. Allow to dry completely before moving.