I've been using a 'terrain wall pillar' lately for post-Elder outposts & bases. It can be done with a single max height pillar if you just have a repair and R&R base or three pillars if you add basic metal processing. Beyond that can just add pillars if needed but at some point you'd likely find it cheaper stone and time wise to use another approach.

For a pillar base, you need relatively flat land (or hilltop) - might have to dig out any nearby high spots, and you make max height (8 meter) pillars. Just make sure that there's no places a Troll can stand that is within 8 meters of any part of the finished base.

To make the actual base - place the fire atop the pillar and use eight of the long core poles radiating from the top of the pillar. At black forest/early swamp levels you can build a 14 meter square base easily. If you add a pair of pillars for kiln and smelter you should end up with a larger T-shaped base.

Tricky parts include making non-portal access viable without having to rebuild them after every raid. I usually make a two-wide ladder 'ramp' with the addition of 45 degree beams and add 'landings' with a chest two meters above ground and every 4 meters afterwards. This allows movement of ore up the ladder from cart by standing in one place and moving the ore from container to container. **

This approach works best with the use of decentralized 'non-base' farms and stockyards.

** Make sure and leave a gap between the top of the ladder ramp and the actual base so that no mob path exists. Also keep ramp supports as far away from the pillar as possible.