Begin by drawing out your main parts to size on a piece of paper or card. Cut these out carefully making sure all ends are square, and use them as guides for cutting your main wooden pieces. If you have made measurements to suit your trunk's contents, test your pieces for fit before you cut any wood.
Sand the edges of all your pieces to make sure the edges are flat and square for the best fit. Test fit the box base and sides before gluing.
If you are going to include a sliding tray or shelf in your chest, check the next step before gluing your basic box together, it may be easier to glue the runners in place before you assemble the box
When your parts are all square, with edges neatly squared and sanded, apply a thin line of glue around the edges of the chest base, then glue the ends and front and back to the base, with the front and back overlapping the ends of the sides.
Set your basic box in a gluing jig or clamp it until the glue dries. Make sure all the sides are square and pressed tightly against the base and the ends of adjoining pieces. Remove any glue that squeezes out when the parts are clamped.