I know of a pattern for slippers that uses three squares, but those are made from crochet. I would think that you could make them a similar way.
The "pattern" for these is more of a set of instructions which are here:
Square 1: Knit/crochet a square slightly longer than the sole of the foot. Turn on point and take two diagonal corners and sew together.
Square 2&3: Make a square the size of the open area of the toe. (Usually this is a 1-3inch square, depending on age of the person you're making for.) Then stitch one square along the edges to the toe of the slipper and the other to the heel. Make a Pom-pom and stitch it to the area where the three corners meet.
These instructions make one slipper. Simply repeat to make second slipper.
Now, I know without pictures that those instructions may be as clear as mud... But hopefully, I can get some pictures of some made to help clarify that set of instructions.
To get to the two square concept that you mentioned... If you took the above pattern and instead of making two of the little squares made only 1 you could make the main square larger and fold the toe corner back towards the arch of the foot. Once you made a now square/boxy end to the front, you could sew the small square onto the back of the heel as in the above directions and that would give you a two square set of slippers.
I hope this helps. Maybe someone can help me clarify my directions to help what I'm saying sound more clear.