Use any color you want and length.
Step 1: Measure
See how long and high you want your box to be.
Step 3: Sides (small)
Make two of them.
Step 4: Sides (long)
Make two of them also and make sure you measure them the same height.
Step 7: Make Flap
Use any color ran out of yellow. Do the same thing like before but make sure that there is enough slack to go down around it.
Step 8: Finish Touches
Use something to hold the flap and box together.
Step 9: Finished
You can use this to put cards in or to hide something it's up to you. Please look at my other deck box they fit nicely in the big deck box.