To make the individual tree bases I simply cut 40mm circles out of Marley tile and then cut 35mm circles from 3mm thick high density foam which I got for free from supermarket pizza base bottoms. The foam was then chamfered to make a seemless rise in the base and glued on to the Marley tile with carpet tackifier which is a latex rubber glue. Once dry I pricked three holes in around the base for the trees to fit into and then took the smaller trees and glued them in place with the tackifier and left them to dry. The process was followed until I had 3 trees on each base and they were all left overnight to thoroughly dry. I must point out that it is best to do this in batches of around 25 to thirty as some of the cutting processes can be quite tedious.
With the trees dry I decided to glue down some rocks with tackifier and left them to dry out so that I could paint the whole of the bases including the rocks with dark brown paint. The rocks were then painted grey and drybrushed with a pale linen colour and various bushes added for effect. Finally the base was again painted brown which was used as the glue to attach the scatter material and that was it.
Here are some pics to show how they look and some figures to give a sense of scale, just click the images to enlarge them.