Fill an empty firebox with logs made from single-face corrugated cardboard, left. Cut one piece of cardboard to desired width and length. (The longer the piece, the bigger the log diameter will be.) With the ridged side facing out, roll the cardboard into a tight cylinder and secure with hot glue. Cut a piece of corrugated cardboard just big enough to fit around the log, then paint the ridged side with flat white paint. When it’s dry, attach the cardboard to the log with hot glue, white side facing out. Use a hacksaw to cut logs at a 45-degree angle to make branches. Attach with hot glue.