Outline half of the circle with the white icing and then run a squiggly line through the middle of the cookie to finish the outline.
This will make the slopes of the hill. Continue until you have finished all of your cookies. Then, with the blue icing, just complete the rest of the circle with the outline.
You don't have to outline the center of the cookie with blue since the white will act as a barrier for the blue flood icing. Continue with all of your cookies.
Then, put the white flood icing in a squeeze bottle. Squeeze a dollop of white icing in the middle of the white outline.
With a toothpick, drag the icing to the edge of the outline. Continue with all of the cookies.
Now repeat, with the blue icing. Let all of the cookies dry before you continue.
Using a pastry bag with a number 3 tip (or use the squeeze bottle if the hole is small enough and you think you can be precise) and make three trees. To do this, I concentrated on just making horizontal lines back and forth, making sure that the bottom one was large than the top ones. Let dry completely.
With a pastry bag filled with the number 1 (or 2) tip, make ornaments with the red frosting.
Then, make the snow with the white frosting. To do this, just squeeze a little bit on the pastry bag and then pick up real fast so that there is no tail on the ornament or snow flake. If I see that I'm about to make a tail, I circle the pastry bag so that the tail wraps around the snowflake or ornament as I release pressure and then the tail becomes part of the circle instead of a nasty line that ruins your picture.
Let dry for a few hours or overnight and then store in an airtight container at room temperature. Enjoy!