Decide in advance how large you want the cedar containers. Make raised garden containers with open bottoms 3 feet wide and 4 to 8 feet long, depending on your space. Make smaller containers for patios no bigger than 3 feet by 2 feet wide. Decide how tall you want the containers, as well. Cedar planks come in widths from 4 inches to 16 inches. Deeper containers accommodate deep-rooted vegetable plants, but cost more to build and fill with soil. Shallow containers work well for raised garden containers because they dry out less quickly and you can incorporate the natural garden soil into the beds.
Measure the planks to the desired lengths and mark them with a pencil. Cut the planks with the miter saw on the line.
Set the planks on the ground to form a box. Drill two holes at the end of each plank to secure the planks together. Space the holes 2 to 4 inches apart, depending on the width of the plank. Make four holes if using 16-inch planks for extra stability.
Insert the screws into the holes and tighten them with a screwdriver. You now have a cedar box that will make a durable, long-lasting container.
Measure and cut a piece of plywood to fit the bottom of the container, if desired. Drill four 1/2-inch holes in the bottom to ensure adequate drainage. Secure the plywood to the bottom of the container with a staple gun.