Here is something to start with...
http://www.rabbit.org/faq/sections/rabbit-proofing.html
I hope the link works. There are a lot of things to think about in having a free roaming rabbit. There are so many things that they can get into. They are a) very smart critters and b) can be VERY VERY determinded once they set their mind to something.
Just because he is always a good boy when you around, doesn't mean that he won't eat the couch while you are gone for the day. And since you have a flemish, they can do some real damage in a very short period of time.
I just have some small breeds, but they can be very destructive. Despite the fact that I have grass mats, hard baby plastic toys (no small parts that they could choke on), wicker balls, wicker baskets, special little bunny mobiles with all kinds of stuff to chew on, wooden cubes, apple sticks, pine cones, boxes...My baby girl Petunia has decided that she wants to see what is under the carpet in every room. I've tried to tell her its just plywood, but she doesn't believe me. Some day when I have new carpet installed, the people won't have much to remove.
Many people on the forum have free roaming rabbits, but its just something you have plan for.