Custom Terrains?

I tried using the box procedural asset to create my own discretized terrain, where i can vary the rigid body properties of this terrain at any place. However, when placing the boxes (precisely) to form a grid, I still see gaps in between. I tried moving objects over this custom terrain, but they get influenced by these very slight gaps and ups and downs.

Is there someway I can counter these gaps and ups and downs?

Thanks!