Making a simple base
First start with a simple, cheap picture frame. I bought this one in a local furniture store. The size depends of course on the subject of your modelling project. Flip out the glass and the backside board.
Now start with the edges. It always looks better to raise the ground work above the picture frame. Cut strips from plastic card, according to the insides of the picture frame.
Glue the strips together to create a frame inside the picture frame. Use superglue.
Fix the back board back into the frame and glue the plastic card frame on to it. This way you will end up with absolutely smooth and ready to paint diorama sides.
Now it is time to start filling the frame with a wall filler or repair paste. Any wall filler will do. Cover the plastic sides with masking tape to prevent the wall filler from ruining your beautiful smooth diorama sides. Don't pay any attention to the brown stuff, that was just some experimenting.
Fill the frame just below the edges. Use a big, wide, flat, wet paintbrush to smoothe the surface
Now it is time to put the vegetation into the still wet filler!!
Sprinkle some dirt, sand with various grains on the filler. Press it gently into the surface
Now comes a tricky part. Press your model gently into the still soft groundwork to ensure a proper set. Do the same with your figures and other items. Now is also the time to create foot- and tiremarks. But be carefull.
You could also carefully drop some diluted whiteglue onto the sand and dirt to fix everything properly.
Leave the base to dry, at least two or three days!!!
Remove the tape from the sides and mask the wooden picture frame. Pull out your airbrush! I prefer Tamya acrylics in my airbrush. Start gently spraying the plastic sides with several coats of semi gloss black. Slowly cover the rest of the grondwork with the black paint. A little overspray is not a dramatic, but be careful. It might be wise to practice first!!.
Now spray over the black ground work different shades of earth color. Work from the darker to the lighter shades, until you are satisfied. Remove the tape en leave the paint to dry for at least one day.
Finished, some snow added, fixed with diluted whiteglue.