Here is my first based building for Second Chance City. It's based on some thin (3mm, sold to me as 2mm) MDF. The only difficulty lay in preventing it warping - basically, I found that so long as I did the same to the underside as I did to the top - glue, paint, etc, it would return to reasonable flatness as it dried. I'm really pleased with the look I've achieved with this, and am looking forward to basing the others. I used a little bit of Woodland Scenics 'Burnt Grass' turf, and some Silflor tufts to add a little vegetation.