In a large mixing bowl, use a hand mixer or stand mixer to cream the softened butter and brown sugar until light and fluffy, about 2–3 minutes.
Add the molasses, egg, cinnamon, ginger, allspice, cloves, baking soda, and salt. Mix until smooth, scraping down the sides of the bowl as needed.
Gradually add the flour to the wet ingredients, mixing until fully incorporated and a smooth dough forms.
Remove the dough from the bowl and wrap it tightly in plastic wrap. Refrigerate for at least 1 hour, or until firm.
Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.
Lightly flour a clean surface and roll the chilled dough to 1/4-inch thickness.
Use a gingerbread man cookie cutter (or other shapes) to cut out cookies. Place them on the prepared baking sheet, leaving 1–2 inches of space between each cookie. Re-roll scraps of dough and continue cutting until all the dough is used.
Bake in the preheated oven for 10–12 minutes, or until the edges of the cookies are set but not darkened.
Let the cookies cool on the baking sheet for 2 minutes, then transfer them to a wire rack to cool completely, about 30 minutes, before decorating.