Question: Cut the front and back base panels.
Options:
Use 1 x 6 lumber and cut two pieces to the width that you cut your bottom panel. Skip this step if making wall if fastening to the wall.
Use 1 x 6 lumber and cut two pieces to the width that you cut your  panel. Skip this step if making wall if fastening to the wall.
Answer: Use 1 x 6 lumber and cut two pieces to the width that you cut your bottom panel. Skip this step if making wall if fastening to the wall.