In A17, i'd normally start with a pillar base of 4 hollow pillars of 3x3, 8 or 7 tall.
I'd use one pillar for hatch-elevator entry, and another with a haybale at the bottom as exit.
Atop of those pillars i construct my early base room, 2 blocks high.
For defense, i've been using centre pole loops in the early game, meatgrinder
of bladetraps as soon as i can craft them. And no, i don't mind using loops. I use
them while i can, knowing they will one day be history.
View attachment 27371
Later on, as i get more materials, i will often add another floor and some more pillars.
Tend to put a bit more work into that upmost floor.
And that is pretty much it. Eventually, i tend to make a perimeter walk, high up. I started
doing those in A16, mostly to access my turrets in an easy way. I might experiment a bit
with spiked defenses, or use a dart-trap+electric fense corridor in newer builds.