Then I covered it in construction paper. (You could easily wrap them with some kind of larger paper or wrapping paper if that works better for you or you want a specific kind of pattern.
The idea is to place something inside the box, hidden from sight and have students blindly reach inside and try to guess what it is. It is also a good way to get them talking and using descriptive words.
This is my "MONSTER BOX". I get out various flash cards... (colors, shapes, letters, numbers, etc.) and lay them out on a table or on the floor. Then the hungry monster asks for one of them specifically and the child feeds the correct flash card to the monster. If the child feeds them the incorrect card, the monster spits it out and states the correct answer, and asks for the first choice again. :)