a cardboard tablet cover? oh cardboard...
Step 1: Measuring
measure your device on a piece of cardboard and add 1cm to both length and breadth.(picture already added with1cm).
do not cut it out.
cut slits on all four sides. Fold up all sides.
measure a hole in the breadth and on the length's tip, cut out the same size of the tip to fit perfectly into the hole. do this for all four sides. If you want to, tape or staple it.