Place an 81-by-2-by-4-inch board on one of its 2-inch sides on your work surface. Attach a 71-by-2-by-2-inch board to the edge of the 81-inch board. Place the smaller board flush against the larger board, centered 5 inches in from either edge of the larger board. Use wood glue where the two pieces meet. Place one nail 1/2 inch in from each end of the smaller board using a nail gun. Place an additional nail every 10 inches for a total of nine nails. Repeat the process with a second 81-by-2-by-4-inch board and a second 71-by-2-by-2-inch board.
Create a rectangle out of the two 81-inch boards from Step 1 and two 61-by-2-by-4-inch boards. Place the cut ends of the 61-inch boards flush against the side of the larger boards. Rest all four boards on one of the 2-inch sides. Apply wood glue where the boards meet. Secure them in place by placing nails through the larger boards into the ends of the smaller boards using a nail gun and 4-inch nails. Place two nails through the larger boards into each end of the smaller boards for a total of eight nails.
Place nine 61-by-4-by-1 inch boards across the width of the rectangle, resting the ends of the 1-inch thick boards on the 71-inch boards from Step 1. Space the four boards evenly across the 71-inch long boards and secure them in place using a nail gun. Place one nail through each end of the 1-inch boards directly into the 71-inch long boards to create the bed slats.
Drill 1-inch deep holes in the side of four 48-by-4-by-4-inch boards. Starting at one end of each board, place the holes around all four sides of the board. Keep them no more than 16 inches from the top end of the board. The holes are to hold actual tree branches so the width of the holes depends on the size of the tree branches. Place the holes at an angle so that when the board is stood upright and the branches are inserted, they will extend upward like a tree’s branches.
Flip the rectangle over, resting the top of the structure on your work surface. On the inside of each corner of the rectangle, place one of the 48-inch boards. Rest one cut end of each board flush with the work surface. Press the board flush against the inside corner of the rectangle. Use the nail gun to drive two nails through the outside of the rectangle into each side of the 48-inch boards. Space the nails 2 inches above and below the edge of the rectangle to secure the four legs.
Turn the structure upright again. Cut a 4-inch square out of each corner of a 81-by-61-by-3/4-inch piece of plywood. Place the plywood on top of the slats. Rest the plywood inside the rectangular frame. The plywood helps evenly distribute the weight of the mattress once the bed is set up.
Apply wood glue to the end of tree branches. Insert the branches into the drilled holes of the tree. The number of branches depends on how full you want the tree to be. For an average fullness, use 10 to 15 branches per wood board. Use branches of different lengths to create a real tree look. If desired, use hot glue to attach silk leaves to the ends of the branches.
Place the mattress on top of the plywood sheet. Because the plywood provides even weight distribution, there's no need to use a box spring. The mattress sits upon the pine platform with four boards sticking up at each corner, with 10 or more branches set in each board to create the tree effect.