Pull off tufts of the green merino wool and lay it over the surface of the polystyrene tree.
Use your felting tool to stab the wool into the polystyrene base so that it sticks. Continue doing this until you have covered the base all over with green wool, except for the very ends of each layer of ‘branches’.
Leave the bottom of the tree blank so that it can stand up.
Use a single needle to stab white merino wool around the edges of the branches.