Cut panels for your box out of the sheet of plywood. You need four sheets at 12 inches by 8 inches, two sheets at 12 inches by 2 inches, two sheets at 8 inches by 2 inches and two sheets at 8 inches by 8 inches.
Sand all the wood and paint it red on one side of each panel.
Separate one 12-inch-by-8-inch panel and all four panels that are 2 inches wide.
Use four corner brackets to assemble the panels into a shallow box, which is the lid. Seal-connect the corners opposite the brackets using four L-brackets.
Use the remaining panels to build an 8-inch-deep box, using the remaining corner brackets and L-brackets as you did with the lid.
Line the inside of both boxes with yellow shelf paper. This both adds color to the interior and helps hold the lid together.
Drill two 1-inch diameter holes 6 inches apart on the center line of the shallow box (the lid).
Run rope through the plastic tubing, then thread each end through the holes in the lid.
On the underside of the lid, run one end of the rope through a washer and tie it off with a knot. You may want to use pliers to get the knot very tight. Repeat for the other side.
Connect the lid to the main box using the hinges. Place each hinge 1 1/2 inches from the outside edge of the box, along one of the longer sides. If you use a third hinge, center it between the other two.
Connect the latches on the long side opposite the hinges, spaced just as you spaced the outer hinges on the back side of the box.