If you need to use a Styrofoam box to place inside a shipping box to keep your merchandise safer and more secure while it is in transit, you do not have to spend a lot of money buying pre-made foam boxes. Instead, you can create a custom-sized box using sheets of Styrofoam purchased at a hardware or craft supply store. Making your own Styrofoam box to measure ensures a box which will fit perfectly inside your shipping box.
Cut six Styrofoam sheets into squares that measure 12 inches on all sides.
Cut one Styrofoam sheet into a square that measures 11 inches on all sides. Set this square aside; it will be used to make the box's lid.
Place one 12-inch Styrofoam square onto a tabletop. This will be the base of the box.
Place two more squares upright against two opposing sides, and tape them into place with duct tape.
Place two more two squares onto the remaining two sides of the base piece, and tape them into place using duct tape.
Place the 11-inch square into the center of the remaining 12-inch square, and tape the smaller square into the center of the larger square securely. This will be the lid. Place the lid onto the top of the box to complete the Styrofoam box.
Make smaller or larger Styrofoam boxes by adjusting the dimensions of the squares you cut.