Business Card Cube Module
This unit can be used to make cubes and almost any shapes built from cubes using business cards. With only two folds, it’s literally the simplest unit I know. Instead of a business card, you can use a rectangle of almost any proportions as long as it’s not quite square (3:2 aspect ratio seems to be a reasonable minimum). Thick paper is recommended. You can also use a square of thin or medium-thick paper and fold it in half.
I used as similar concept for the basic “volume-building” module in my Building Block Unit family, with additional units added for decoration and for building less cube-like shapes.