Use an empty tissue box is long and rectanglular. Some tissue boxes are upright squares, which won't work for this project.
Cut brown construction paper to fit each side of the tissue box, and use glue to hold it in place. Be generous with the glue and allow it to dry.
Cut the tissue box on the front and two sides, about an inch from the top, so the pirate's chest can be opened. Start on the left side and work your way around to the right. This will allow you to put goodies inside the chest.
Cut out some gold construction paper to decorate the corners of the tissue box. You also will want to cut a small square for the front center of the box. Glue these in place.
Paint a black keyhole on the gold square in the middle of the box. Paint a message in black on the top of the box as a warning to would-be looters. Paint something like "Beware".
Paint a skull and crossbones in white underneath your message to scare anyone who might be thinking of touching your treasure.
Glue some gold fabric inside of the pirate's chest. This will make the inside of the chest glow or shine when opened. When the paint and glue dry, your pirate's chest will be ready for use.