What's the best way to glue/adhese the street baseplates to a plywood table? I'm building a Lego city, and I want to permanently glue the road onto the table.  But I don't want it to be "lumpy", or melt, and I want to make sure that the baseplates will not come off the table, whether it be water or indirect heat (such as sunlight).  A friend suggested furniture glue, but I'm not sure that'll be strong enough or flat enough. 

Any ideas welcome.
You could always put a screw through a 2x2 plate and use it to fix the corners, the rounded corners on the road plates won't be damaged, and you only lose a very small, cheap part.