Hi
I've just completed completed the 50n hour course and am sorry to say that this is my first time on the forums.
I still find it hard to tell the difference between these two. As near as I can figure, controlled practice is when the teacher has to start the exercise or give constant instructions For example, a game of Simon says or if you give them a gap fill exercise.
Free practice is something like a debate or a discussion. You may give them a topic but you are not providing the answers or the questions. It is all the students' own ideas. It can also be a role play where you have told one student to give the other student advice on a problem that the students have thought of themselves. Although in this case you are giving them the role play it is left to them to decide exactly what to do and say.
Don't know if you still need this or if it helps.