Ever look at a miniature and say to yourself, "Nice figure, but what the heck is that pile its standing on?" Unfortunately it's fairly common to see sculpted rocks formed into a rounded pile or piles. The details frequently look organic and squished. In short, like elephant poo.
The good news is there are quick and easy alternatives that do not require the expertise of a master sculptor. This is by no means meant to be an exhaustive list. Mainly because I'm way too lazy for that.
The first method is the easiest. Small pieces of redwood tree bark work great as rocks at the 28mm level. They look best when they are partially embedded into the terrain. Below are two examples of this type.
For the rider of Rohan, first the pieces of bark were glued down. Then the rest of the base, mostly the rear, was bulked out with green stuff to the desired size. Once the putty had cured, sand was superglued over most of the base (with the exceptions of the exposed rock, skull, and arrow. Once the glue had dried, The sand was sealed with watered down Elmer's glue. Once that had dried, the base was primed and painted. Static grass was added as a final touch.
The base of the Leman Russ figure was done in much the same way with the exception that the putty(white stuff in this case) was left exposed (as snow) in the final version rather than covered with static grass.
The advantage of using redwood bark is that it is quick, cheap, and easy. Bags can be purchased at pet stores or in the gardening sections of hardware or drug stores. It is soft enough to easily pin through. The disadvantage is that using redwood bark gives you relatively limited control over the size and appearance of the rocks.
A second method is to carve, rather than sculpt, rocks out of cured putty. The first step is to create a rough mass of putty in the general shape of what you'd like the finished rock to look like. Since you will be carving away from the mass, remember to make it slightly larger than you need. Step two is to take an exacto and start hacking away. You want the cuts to be irregular in order to make the rock appear natural. Of course this technique could also be used for man-made stonework on the base. It's often easier to get sharp edges through carving rather than through sculpting.
The base of this Tyrion model was created through carving hardened masses of putty.
The third method of creating rocks is a two part process. It involves taking impressions of actual rocks, First of course, you need a rock. Second you need to create the general shape of the rock on your base with putty and allow it to cure. This will need to be slightly smaller than the desired size since we will be adding another layer. Once the first mass has cured, you will be adding a thin layer of putty ( roughly 1/16th to 1/8th of an inch). Next you will be wetting your real rock. You can lick it if you want to, but I'd recommend dipping it in water. Once wet, press the rock into the putty creating your impression. You will of course end up with the negative of your real rock. If you want the exact texture, you will need to make a press mold of the rock and then use that mold to create the texture for your base.
The purpose of the first mass is to provide you with a solid foundation for the second layer. If you try to do the whole thing in one shot, you end up distorting one side as you apply pressure to the other side. You'll only end up frustrated.
As far as painting goes, the rocks in the images here were basecoated black and either white or bone was added gradually for several layers of increasingly fine dry brushing
So there you have it, a few new tools to aid in your basing adventures. Don't step in the poo on your way out.