Step 6: Marking sides

Picture of Marking sides
Now you should mark the sides (it's not a dice without the numbers).
Take the marker and mark opposite sides this way 1-6, 3-4, 2-5.
2 goes on the right of 1, turn the dice so 1 is facing you and the first right side to the 1 is 2.

And "viola" there is your dice.