One of the main things is to put proper drains in, they are everything and if you have the best surface in the world it won't be any good unless the drains are good. It sounds ideal fencing off an area and then putting hardcore down and some sand but it won't be enough - or rather it won't last very long (unless you have exceptionally dry weather and good draining land).
Also as Eml says, do get planning permission, it all depends on where you are and you are better checking than not. If you do something which permanently changes / alters the landscape then technically you need to obtain the relevant permission.
And believe me, if they catch you and don't like what you've done they will make you put it back just as it was before, ie to a field.