Anything that touches the ground, a tree or a big boulder will reset the structure strength.

Use the hoe to build gigantic ground pillars for support.
Planting trees is a fragile, but tall option.
The swamp has gigantic ancient trees that can't be cut down.
The plains has gigantic stone pillars that can break.
A mountain cliff is an opportunity to anchor against a wall.

The strongest skeletons are built from iron doors or iron wood beams. Either way is roughly equal, but the doors can be easier to set up.