I did a small 30 cm * 30 cm terrain tile as an excecise for the Port republic table, have a look:
I just quickly took the picture outside without optimization or anything, but I hope you get the idea. The basic structure is cardboard elevation levels glued on top of a wooden base. The cardboard levels were cut and then glued on the base on a hot glue gun. The river was cut into the cardboard afterwards. The whole surface was then covered in two layers of acrylic caulk to hide any cardboard. It gives the surface a nice, soft, rubbery texture, so it won't crack in use.
Then, I glued some sand to select places. You don't need sand in places where you put down flock later on, so there's no need to put sand all over the model. In 6mm, coarse playground sand can be used to represent areas of rocks. After the sand, the whole piece was spraypainted brown. I then heavily drybrushed the brown areas with light brown and then with mustard yellow. Again, the areas which will be completely covered in flock can be ignored.
Now for the flocking. I have some different colors of flock by Woodland scenics and noch. First I glued a "basecoat" of neutral green flock over the piece, leaving some areas with a bit of gorund showing. Then I used a glue spray to attach two other types of flock here and there on top of the base level. This seems to work well with the glue spray. Finally, I glued a piece of that spongy brush stuff here and there to represent undergrowth. The areas of coarse sand were given a khaki and cream white drybrush. The fence is made of plasticard and the "crops" inside the fence are regular static grass on top of this stuff which is a bit like sawdust. The road is just unpainted sand I have glued on the base (without flock underneath).
The water areas are made first by painting a few successively darker brown colors building to almost black where the water is deep. It is then covered with "realistic water" in the lake and "water effects" in the river.
Now, lessons learned:
1: The cardboard levels are otherwise ok, but they are a bit on the thick side. This is most evident with the river, which looks like it is in a very deep groove in the ground.
2: When doing water, first put all "realistic water" and after it has dried, do the water effect areas. You can see a bit of cloudy color in the middle of the lake. That is water effects which was trapped under a layer of realistic water and hasn't become all clear yet. Also, be careful not to make any flock or static grass come into contact with the realistic water, as it will become sucked in and soak your grass. I tried to do an area of reeds or something on the shore and the realistic water just enveloped the static grass immediately.
Ok, I have already cut the base for the port republic table and am tracing the elevation levels to it. I suppose with these techniques it'll turn out just fine.