Well, given that there is no central "keep" this models as more of a guard fort or strong point.
Which is good, as it decreases the amount of ground work needed for moats, galcises, redoubts, ramparts and the like.
A simple berm would likely suffice, with a wooden palisade upon that. That would allow modeling some impedimentia before the berm, upon which siege machines might be foundering (or succeeding).
The berm ought to be about as tall as the base for the fort. The slope should be no more than 40 degrees, so it ought to be about twice as wide as deep. It can be very appropriate to have water running in it (unless one is modeling a Crusader fort, naturally).
A person could model a forlorn hope set against a breach in the palisade; said hope might be either succeeding or failing (sealing up the breach with their dead, to use a well-coined phrase) to good effect.
One could set the fort to one side, at a middle height in a dio, with a force of mounted knights set to sally over the hill and into the raiding host attempting to invest the palisade, too.