Place the usb over the inside of the pieces and mark out its shape. Cut out this shape through the first layer and foam but leave th paper on the outside in tact. do this for the lid asweel but only the for the top part of the USB (the lid). Now remove the cut out section to leave a space where the USB will fit when the pieces are placed together. Glue the two pieces together and the two sides of the lid too.
NOTE: don't cut through outer layer of paper, this will ruin the outside