Level the ground surrounding the deck. Measure to the lowest point of the ground at the edge of the deck. Use a shovel and rake to level the rest of the ground to this level. Use a level to ensure the ground is as even as possible.
Measure between the support posts of the deck to create a bottom support for the skirting. Purchase 2-by-4-inch boards to place between each post in the measured length.
Attach 2-by-4-inch boards between each post at the ground level. Nail in place using 6-inch nails to ensure support for the skirting.
Cut or order skirting in the needed measurements. Cut plywood or lattice to the length to fit between the supporting posts. Cut the width to fit from the bottom of the deck to the ground. Order vinyl- or polymer-based skirting in the desired size.
Attach the skirting by using a drill to place 6-inch screws in the top and bottom of the pieces of lattice. Place screws approximately every foot into the bottom of the decking and the bottom support wood.