Cut 1-by-6 fence boards, using a circular saw or table saw, to the following dimensions:
Six boards at 2-1/2 feet
Four boards at 1 foot
If you're using another dimension of lumber, such as 1-by-8 or 1-by-10, you will need to adjust some of the measurements for the bottom and sides of the box.
1-by-8: cut two boards 2-1/2 feet in length and four boards 16 inches in length
Rip 1-by-1 strips of wood from a 1-by-6 and cut it into the following dimensions:
Four 12-inch pieces with the ends cut at 45-degree angles
Four 28-inch pieces with the ends cut at 45-degree angles
Four 8-inch pieces
If you're using 1-by-8, cut four more 10-inch pieces (without angles) instead of 8-inch pieces.
Assemble the frame of the box by attaching the 28-inch angled pieces to the 12-inch angled pieces at the corners. Tack these together with nails to build the top and bottom of the frame. Use the 8-inch pieces to attach top and bottom frames to each other.
Attach the 2-1/2-foot boards horizontally to the long sides of the frame and the 1-foot pieces to the short sides of the frame. Tack on the bottom boards to the bottom of the frame.
Sand and paint the outside of the box if desired.
Fill the planter box with dirt and plant flowers, herbs, vegetables, or greens in it.