A classic small beer is made from a later gyle of a bigger beer; that is you make a very strong all-grain batch of beer, like barleywine, and then re-sparge the leftover mash to collect what little sugar is left. This results in a pretty low gravity wort which you can ferment out to a nice easy drinking session beer. This technique, called partigyle, is a very traditional way of brewing, and it allows you to make the most beer of the ingredients you have. Also, it gave innkeepers a way to make beer they could serve to their patrons in large quantities, cheaply, without causing a riot every night.
The easiest to find example of this would be Anchor's Small Beer which is made from the late runnings of their Old Foghorn barleywine. Most traditional British breweries use this to make multiple different beers as well.
In my opinion, it would be fairly difficult to recreate a small beer in a single batch, but the best way to do it I think would be to find a recipe of a strong beer you like, and then scale it way way down, shooting for a max OG of around 1.035.