Glue the Roof in Place
When your interior is to your liking, run a bead of glue along the upper edges of the walls and glue the roof of your roombox in place. Make sure all the edges of the walls line up with the outside edges of the roof.
Trim the Walls and Roof True
When the glue is dry, use your sharp knife to trim the outside edges of the roombox, making sure there are no protruding edges. Check that all seams are securely glued.
Paper the Outside of the Roombox
To make sure the seams of the box are secured, apply a paper coating to the outside of your box. If the box will not be seen you can use kraft paper or plain wrapping tissue.
Cut a strip of paper long enough to go around the side walls and across the back of the box. You may need to make a join in decorative paper on the box back where it won't be seen. The paper should be the length of two sides, plus the length of the back, and it should be two inches wider than the sides. Check the fit of the paper by lining it up with the front edge on one side and taking it around the box, bending it gently at the back corners. When you are sure the paper is the correct size, apply glue to the sides of the box and wrap the paper around the sides, lining up the paper with the front edge, making sure one inch is below the bottom of the box and one inch is above the box ceiling. Smooth the paper in place
Trim the corners and turn the edges to the top and bottom of the box Trim a triangle from each of the corners and make a neat fold, taking the excess 1 inch of paper and gluing it to the top and bottom of the box. Set the box aside to dry.
Cover the top of the box by cutting out a section of paper that will completely cover the box top. Apply glue to the top of the box and glue this final piece of paper in place.
Set your box aside to dry, and finish it as you wish.