Instructions
Measure the height, width and depth of your PSP. Measure the screen opening. You will need to cut out an area so you can see your screen. Draw out flaps on the top and bottom that fit into each other, just like the lids of cereal boxes close.
Gather a piece of cardboard larger than the total area size of your PSP. Use the box the PSP came in if you still have it.
Use a ruler or other straight edge to draw out the dimensions of the PSP on the cardboard. Allow for folds and the thickness of the cardboard. The final drawing should look like your PSP if you took the cover off and spread it flat. Add an opening where it can slide in and out.
Cut the excess cardboard away. Scissors leave straggly edges, so use a straight razor for clean lines. Use a flat edge to help fold along the lines. You will need to make the fold as sharp as you can and crease it so the sides can stand up.
Place marks on the inside of the cardboard for the trigger buttons as well as the strap, then cut them out. Also, you'll need to make holes for the screen and front controls. Paper clips can hold the sides together while you fold and measure the placement of the cutouts.
Glue the sides together once you're comfortable with the snug fit and cutouts of your carrying case. Wood glue will keep the cardboard together better than household glue. The paper clips will keep the case together while it dries.
Decorate the cardboard however you like. Use fabric, ribbons, jewels, even colorful duct tape. You can use Velcro or buttons to fasten the bottom of your PSP carrying case.