Basics:
You want to start with the most stable foundation that is colored blue. You can flatten the terrain using the hoe, just stand where you want the height of the ground and then move the hoe around (the hoe changes the ground based upon the height you are standing at). Make sure all your foundations are blue by using the hoe. This will help ensure more consistent stability.

If you want to go big, then you need to start with stone or iron poles as these give more stability and allow you to build higher. But the higher you build (lessening the stability) the smaller the room will be as it gets harder to have enough stability to roof the area.

For instance, in this screenshot, in order to cover 8 blocks horizontally (1 block being a 1x1) I could only build 10 blocks high before I ran out of stability to cover the distance with the stone arches. The very bottom piece of the pillars is just for show and clipped into the ground. And for clarity, I did run tests before I actually started building this room.
https://steamcommunity.com/sharedfiles/filedetails/?id=2812632640

Clipping is what really allows you to get creative and it’s also extremely important on what your cursor is pointing at when you build. In this screenshot, I clipped the fence into the ground (trolls cannot walk over it) by placing wood beams and then placing my cursor under the wood beams when placing the fences (the beams on the fence are just for showing the build process).
https://steamcommunity.com/sharedfiles/filedetails/?id=2812633058

Clipping can also be used for more stability. For my pyramid,
https://steamcommunity.com/sharedfiles/filedetails/?id=2518693676
I clipped in the stone arches (seen in the middles of the four sides) as stone arches give more stability above them then a stone block when doing a Corbel arch like this. I did do a full scale test of how large I could make this inner room before I started building the pyramid.
https://steamcommunity.com/sharedfiles/filedetails/?id=2812632723

Advanced:
If you want to get into more advanced clipping, then I would suggest starting with trying to make circles. For this type of clipping, you actually want to have your cursor looking at the ground and then the game will calculate a clipped placement. Place a 2x1 brick down, then place another, rotated once by looking at the ground next to the placed brick.
https://steamcommunity.com/sharedfiles/filedetails/?id=2812648731

Once you know how to create a circle, then you can put the circle anywhere and build off of it. For this dome temple thingy,
https://steamcommunity.com/sharedfiles/filedetails/?id=2812644784
I built the circle out of stone arches (the lower outer ring of arches)
https://steamcommunity.com/sharedfiles/filedetails/?id=2812644842
and then raised that circle to be on top of the pillars and then I kept attaching stone arches until the center was filled. The final pillars you see however are not the original pillars during building as I rotated and free placed these pillars to be in the middle of the brick.

You can also attach multiple pieces to the same point. For this water well, multiple points have 3 pieces attached.
https://steamcommunity.com/sharedfiles/filedetails/?id=2592205105
Just look at the attach point and rotate the piece. Here’s 12 attachments to one piece (I deleted the center support piece after it was done). 100% vanilla.
https://steamcommunity.com/sharedfiles/filedetails/?id=2812686229

If you do want to get tricky with things, then you will probably have to free place some objects. To make this couch, I free placed the benches and the couch part by the player legs so the legs would fall down to the ground.
https://steamcommunity.com/sharedfiles/filedetails/?id=2592205175



As a final thought about building…for me, functionality is extremely important, otherwise the building just becomes a piece of art that I will rarely visit again after it’s done. So I’ve broken the game down into as many possible functional buildings that I can. For instance, here is our town of Tombstone.
https://steamcommunity.com/sharedfiles/filedetails/?id=2448968900

And here are the functional buildings.

A building for (left to right) 1)trophies, 2)oddities like boss summons drops, 3)stone, 4)workbench and relevant storage and then 5)wood.
https://steamcommunity.com/sharedfiles/filedetails/?id=2812632793
Across the street is the 6)max resting buff room, 7)boat supplies which leads to the boat dock, 8)the forge with all the smelters behind it and relevant storage then 9)old gear.
https://steamcommunity.com/sharedfiles/filedetails/?id=2812632851
https://steamcommunity.com/sharedfiles/filedetails/?id=2812633015
At the intersection is the 10)“Trading Post” where we hold gear temporarily and where we put stuff that we want to eventually move somewhere else. For instance, there is no 11) cooking in Tombstone. We also have the 12) bank for all the valuables.
https://steamcommunity.com/sharedfiles/filedetails/?id=2812632902
And finally is the building for 13) farm supplies and then the 14) teleporter building.
https://steamcommunity.com/sharedfiles/filedetails/?id=2812632954

We like to have one spot for cooking which we have at our newest base, which also contains our latest 15) personal home (for storage).
https://steamcommunity.com/sharedfiles/filedetails/?id=2676966035
I’m currently building 16) cartography room, to make it like a war room.
https://steamcommunity.com/sharedfiles/filedetails/?id=2812673751
This base also has a 17) livestock pen and building.

I do play with friends, which maybe changes your perspective on what are useful buildings from a solo player and I do have a friend that thinks it’s too tedious to run around to all the separate locations and it can be. But, overall, I consider it a price to pay if you want to make large builds with functional areas.

Our most extreme is what we call Cliff’s. Which became so tedious to run to all the functional areas that we eventually put in teleporters.
https://steamcommunity.com/sharedfiles/filedetails/?id=2677034547