I have a hard time looking for all degree 3 FSPs(By factor square polynomials I mean This) because I found even though I am able to classify irriducible FSPs of degree 3, some other tricky reducible ones, like $x^3-1$, are reducible but cannot be expressed as a product of degree 1 FSP.
So How can I give a list of all degree 3 and 4 FSP?