Apply wood glue to one end of one of the cut pieces of chunky slat. Set it in the middle of the inside of the largest decorative box, and hold for a minute to help secure it.
Apply glue to the top of the chunky slat that you just glued down. Center the middle size decorative box on top of the chunky slat. Gently press down to allow the glue to bind.
Apply glue to one end of the remaining half of chunky slat. Set it in the middle of the inside of the medium sized decorative box, and hold for a minute to secure it.
Apply glue to the top of the chunky slat that you just glued down. Center the smallest decorative box on top of the chunky slat. Gently press down to allow the glue to bind.
Allow to glue to set and bid everything together overnight.
Squeeze some white paint out of the bottle onto a paper plate. Dip the very tip of the fam brush into the paint, and lightly apply paint over the entire structure. You do not want a full layer of paint, make sure to paint it lightly, for the white washed effect.
Allow paint to dry, then fill the boxes with decorations.