I love surface forts. I tend to build castles above-ground.
Yeah me too.
I like to embark with 3 woodcutters 2 miners and 2 farmers.
Get the woodcutters to clear a large area for the castle, mine out a chosen type of stone and lots of it, I like marble recently, then get the miners to turn it all into blocks, while this is happening the farmers and woodworkers set up the mead hall and farms, then I make a farm house for milking, shearing, butchery etc.
By then the first wave of settlers come, usualy with some useless kids, I tell all of them to become farmers and builders, then build a 2story barracks and burrow the kids in it.
By this point im in the first cavern layer and have made hundreds of cage traps.
I set them up outside and in the caves.
My wall starts at this point.
I often make is too large thinking of the future, it takes a few years to set up properly the design is a 2 high wall with a 2 wide walkable perimeter, 3 high towers with fortifications for archers, all surrounded by a 2 deep moat and one gate with a drawbridge with metal bars both linked together, by this point I often have 70ish citizens. I will create a mini village to occupy the gate and open it when needed,
My military often walk the perimeter
Lately I have been thinking of making a military fortress, having rotating training schedules so all farm and then train and then are on duty.
I will often build a fort next to major rivers to reduce the amount of walls needed