Using a serrated knife carefully and slowly cut the ice cream down to preferred size.
Pay special attention to how hard you are pressing while sawing back and forth. Rotate as you cut for a cleaner cut.
If it's not perfect that's okay we can fix it with buttercream.
Add about ½ cup of white frosting to a piping bag fitted with a 1M tip
Starting in the center pipe a star, now make a circle of frosting around the star (creating a rosette).
Be sure to apply even and steady pressure the entire time. Place ice cream cones into the frosting and make sure they stand straight (you may have to add a little extra frosting to one side then another to balance it.
Dye remaining icing green and add to a piping bag fitted with a small star tip.
Starting at the bottom of the cone, pipe the tree with stars. Add sprinkles or dust with powdered sugar
Notes
Pro tip: To avoid stars with "tails" Squeeze, stop squeezing then pull away.