Thanks Marc, here's a few more progress pics for you to enjoy.
The first two shots show the base, which is a simple pine box I bought at my local hardware store for $5. I cut it on an angle to represent the side of a communication trench. The trench wall has been covered with celluclay mixed with tallus, white glue and some burnt umber acrylic paint and a bit of water to create a sloppy goo that I can spread around.
I intend to fill the bottom of the base with celluclay and build it up to level of the cut at the front. The figure will stand in the mud up to his knees.
As you can see, I've started to dirty up the figure using pastels and some of the leftover celluclay mix. I want to figure to look like he lives, sleeps and works in this mud all day long. When the mud dries completely, I'll add a series of oil washes over the muddy patches to blend the colours together and create streaks and splashes. The stretcher has had no weathering done on it yet.