All your basing R belong to US

Now ladies and germs, have a look at this photo of what a part of the road looked like after a heavy rain. Notice all the nice little rocky bits? Cheaper you can't get. But how you say does it go from the road to your miniature base? here is my quick and easy solution

cut a decent sized hole in the bottom of an empty plastic container. in this case i used an old margarine tub.

now make some filters by drilling loads and loads of holes into pieces of plasticard that has been cut to fit into the bottom of the plastic container

 

 like so :)

 now just take your mixed road gravel and in stages sift the different sizes of little rocks apart until you have many different sizes of little rocks to use for all your basing needs