An individual was im pressed at my "Hoth" diorama and asked if i could explain how i did it, so here goes.
The first step is to get a good quality board for your base, i used a 12x24x5/8 prefinished shelf from Lowes with the plastic coating or you can get the faux wood coating, i think it cost me around $6.00, the reason being that the materials used in making this dio uses water and the plastic coating repels the water so it wont soak in and warp yuor base.
next with a pencil mark where you want rocks or humps bumps and what ever you want, get some news paper or foam and secure the stuff onto the board.
Next your LHS should have some Woodland Scenics products there get a roll of plaster cloth that is used mostly for RR, cut the cloth in strips that you can easily manage and wet the cloth and apply to the surface and onto the humps and bumps and whatevers ya got and let dry.
Next get some Mod Podge craft glue puzzle sealer, Wal-Mart sells it, and get a small container of white acrylic paint and mix into the sealer real well brush onto the plaster cloth, this sealer is also a glue which will help secure the plaster cloth to the slick surface of the board, be sure to fill in the small holes from the cloth, and let dry.
Next you will need a container of micro balloons or "snow" from Woodland Scenics from your LHS, get your Mod Podge and spread a second coat onto your board and once you do that put on some latex gloves and shake the "snow" onto the WET sealer until you have a nice thick coat of snow, next "pat" it down lightly into the sealer, let dry, shake off the excess.
Next repeat the above if necessary to achieve thickness.
The ares around the at-ats feet was done with Milliput epoxy putty to build it up before i applied the Mod Podge and snow.
Here are some pics:
http://img.photobucket.com/albums/v602/Stipp08/100_0749.jpg
http://img.photobucket.com/albums/v602/Stipp08/100_0748.jpg
http://img.photobucket.com/albums/v602/Stipp08/100_0751.jpg