Step 1: Cut Side Pieces of the Garden Box

 Cut four (4) Trex boards at a 45-degree angle to be 5 feet long from tip to tip. These will create the two long sides of the garden box.

Next, cut four (4) Trex boards at a 45-degree angle to be 3 feet long from tip to tip. These will create the two short sides of the garden box. The 45-degree angle will allow you to hide the exposed ends of the boards.

Step 2: Cut Deck Boards for the Interior of the Garden Box

First, cut 12 short pieces of the decking to 11 inches long. These pieces will be mounted inside the garden box, and the side pieces cut in Step 1  will attach to them. 

Step 3: Build the Corners 

Attach two of the 11 inches pieces together to form a corner with the 2 inches composite deck screws that are colour matched to your decking. Repeat this process to form 4 corners.

Step 4: Attach the Long Side Boards

Stand the corner pieces on a flat surface. Place the first long 5 feet piece against the corner piece with the short point of the 45-degree angle at the edge of the corner piece where the two 11 inches pieces meet together. Fasten the 5 feet piece to the corner piece with two 2 inches colour-matched composite deck screws. Repeat this process on the other end of the 5 feet piece.

Place the second 5 feet piece on top of the sides you attached in Step 4 and fasten to the corner pieces with two 2 inches colour-matched screws. Repeat this process on the other side to create two 5 feet long sides.

Step 5: Attach the Short Side Boards

Place the first 3 feet piece against the corner pieces attached to the longer pieces. Fasten two 2 inches colour-matched fasteners through the 3 feet piece and into the corner piece. Repeat this process on both ends and for the top 3 feet long piece. Repeat this process on the other end.

Step 6: Add Supports

Place two 11 inches pieces equal distance apart and fasten them to the 5 feet long pieces with two fasteners per 5 feet board. Repeat this process on both sides. These supports will brace the long pieces so they don't push out.

Step 7: Create Top Surface

Cut your top pieces to the desired length for the overhang you would like.

Cut the two longer sides to 5 feet 3 ½ inches to the long point of a 45-degree angle.  

Cut the two shorter pieces to 3 feet 3 ½ inches to the long point of a 45-degree angle.

Fasten these pieces through the top into the side of the upright boards. Fasten every 16 inches with the 2 inches colour-matched composite deck screws.

Step 8: Add the Final Touches

Place the raised garden bed where you intend to keep it. Then, line the box with a weed mat material on the bottom and the interior sides of the garden bed. Fill the Trex garden bed with soil and let the gardening begin!