Cut the base plywood to size and drill 3/4" pocket holes around the edges. Cut the base frame pieces to size and attach them to the plywood with 1 1/2" pocket hole screws and wood glue. The top of the plywood should be flush with the top of the frame pieces.
Cut the bottom support pieces to size and drill 1 1/2" pocket holes at the ends of each board. Attach them to the bottom of the bottom base with 2 1/2" pocket hole screws and wood glue.
Cut the casing to size and attach it to the base frame with 1 1/4" brad nails and wood glue.
Cut the second base plywood to size and drill 3/4" pocket holes along the edges. Cut the frame pieces to size, drill 3/4" pocket holes on the front edges and attach them to the plywood with 1 1/4" pocket hole screws and wood glue.
Center the second base on top of the first base and attach it to the plywood with 1 1/4" pocket hole screws and wood glue.
Cut the trim to size and attach it to the second base frame with 1 1/4" brad nails and wood glue.
Cut the third base plywood to size and drill 3/4" pocket holes around the edges. Cut the frame pieces to size, drill 3/4" pocket holes along one edge of each board and attach them to the plywood with 1 1/4" pocket hole screws and wood glue.
Center the third base on the pedestal and attach it to the second base plywood with 1 1/4" pocket hole screws and wood glue.
Cut the trim pieces to size and attach them to the third base frame with 1 1/4" brad nails and wood glue.