Separate the pine studs into eight 2-foot fractions, four 1 ½-foot lengths and four pieces to use as cross braces. It is always better to first make the box and then cut the cross brace pieces. Make a square with four of the 2-foot pieces and using wood glue, stick them together. After that, use wood screws to secure them. Use the same process with the remaining four pieces.
Glue the pieces
Place the 1 ½-foot pieces in every corner of one of the squares standing up. Remember to glue and screw them together. Press the square with the 1 ½-foot pieces on the side and move the second square over the vertical 1 ½-foot pieces. Glue and screw the other square to the vertical pieces in order to make it look exactly the same as the bottom square. Once you have completed this process, place the box back up on the bottom square and carefully put in the cross bracing. The simplest way to do this is to install a piece of 2 by 4 across the box diagonally, identify the place you want it and then make the cut.
Cross bracing and final touches
When you cut the piece, be sure to glue and screw it to the box as you slide to the second piece. Be sure the cross bracing on facing sides is in the opposite way. Put the plyo box top down on the plywood and mark it before cutting it. Cut the plywood and glue it to the top of box and place screws in the corners.