Making my own game board

Going to start a new project, making a game board to play on at home. There are several issues with this that will need to be overcome -

 - Limited space to set up - I live in a very small flat so I am looking a making a 30" by 30" board that breaks down into 15" pieces for storage.
 - Limited storage - Everything needs to fit in one box or flat pack to go under the sofa.
 - Limited cost - I want this to be as cheap as possible, so will be "acquiring" most of the materials from anywhere I can.

So with this in mind I have come up with this plan -

Each on the tiles is going to be made of cardboard, as I have access to a nearly unlimited supply of cardboard boxes. Each 15" x 15" tile is going to be a sandwich of 2 layers of card, with more are less in places to allow for things like water and hills.

Hoepfully this will explain things a little better - 

Will post work in progress photos when I actually start construction of it.