I'm creating a program for a four motor robot, that needs to follow a square shaped path without lines to guide it. How should I go about this? I've already attempted simply timing the straightaways and turns, but the numbers are finicky, and the robot doesn't respond accurately every time. It has to trade off sweep turns and point turns, and go along the path indefinitely. Any help is greatly appreciated.

Have you tried encoders/do you have access to them/are they allowed?

Encoders are allowed, yes.

Put encoders on the motors. Then, instead of timing the straightaways and turns, simply wait until the encoders reach a certain value. Of course, one motor still might spin faster than another, but this is generally more accurate than just using timers.