Prepare cookies as directed on package or according to your favorite recipe. Cool on baking sheets for 2 minutes; remove to wire rack to cool completely. Cut each cookie in half for a total of 48 halves.
Frost the bottoms of all cookie halves with frosting. Place 6 marshmallow teeth around curved perimeter of 24 halves. For additional support, an additional marshmallow can be placed behind the teeth. Top with remaining 24 halves just slightly behind the marshmallows so that they show. Insert two almond slivers in between teeth for fangs. If fangs do not adhere, dip tips into frosting.