Slow cooling is better for crystal formation. A domestic freezer (-18°C or colder) - sometimes preceded by refrigeration - has worked for thousands of people so you don't need to reinvent the wheel here.
A styrofoam cooler containing cups of liquid nitrogen would be constantly venting asphyxiant gas so you'd better not use it in a confined space.
“There is a way of manipulating matter and energy so as to produce what modern scientists call 'a field of force'. The field acts on the observer and puts him in a privileged position vis-à-vis the universe. From this position he has access to the realities which are ordinarily hidden from us by time and space, matter and energy. This is what we call the Great Work."
― Jacques Bergier, quoting Fulcanelli