you might look at some of the tractor coop-design pages -- they are typically designed for 4 or fewer chickens, and some would be ok as stationary small coops. Basically though you don't need a design as such <g> just a box, probably 4x4 and at LEAST 2.5 ft high (ideally higher, so you can have a proper roost with room below it). You can have it raised on posts or platform so it's a convenient height for you to reach in and clean etc. That also allows you to have part of the run extend underneath the coop, good for inclement weather.
Be aware that it is much harder to run a good dry well-ventilated SMALL coop in winter weather. Not that it can't be done, but it is harder, requires more forethought and management and site selection, and may result in poorer air quality despite your best efforts. Consequently, even if you are legally restricted to just a few chickens it may still pay off to build the largest coop that is practical, just because it will make MANAGEMENT much easier and more pleasant.
Have fun,
Pat