Start by filling your bucket with spray foam and let it expand.
Use hot glue to attach the moss to the top of the foam.
Start by adding the large poinsettias. Put hot glue on the end and add one flower to the center, front, and back of the arrangement.
Next, take the pine stems and trim them. Add a pick to the end of each, dip it in the glue pot, and add evenly to your arrangement.
Here's where things get less structured. Select different Christmas stems, trim them, add a pick, and then use hot glue to add them to your arrangement. Alternate your colors and evenly space them through your arrangement. Continue to fill in the remainder of your arrangement until it is beautiful and full.