The first step in building a strawberry box is to select a 3-foot by 4-foot area outdoors that receives full sun, according to SFGate. Mark it off, and dig a 4-inch-deep rectangle of that size. After digging the hole and tamping the soil, lay down landscape fabric followed by hardware cloth to help keep weeds and animals, such as moles, from coming up through the bottom.
Four 12-inch pieces of 4-by-4-inch lumber are needed for the corner posts. The strawberry box also needs four 3-foot pieces and four 4-foot pieces of 2-by-6 lumber for the ends and sides.
Place a 3-foot-long end piece on its side and a corner post on one end of the board, making sure that the edges are flush. Then, use a screwdriver to drive two 3.5-inch number 14 wood screws through the end piece and into the corner piece. Repeat with another post at the end of the same board, and repeat the process again with the opposite end piece and posts. Attach the two other end pieces to the secured end pieces by screwing them into the posts.
Then, align a side board with one of the end pieces, and secure it to the corner post with two more screws. Attach the other end piece to the other end of the side piece. Repeat this process with a second side board. The final two side boards are then secured on top of the first two. Then, place the box over the hardware cloth, and fill it with soil before planting strawberries.