Plains enemies will tear apart wooden structures. If you expect them to attack, you want your buildings made in stone. Terrain cannot be damaged by mobs, so raised terrain walls or a moat are your best bet for keeping land-based enemies out. If you keep wolves or boars at your plains base, keep them sheltered to prevent losses to Deathsquitoes.

A lot of this stops being a concern if you build in a high elevation of plains. You may find some places that count as plains but start to have the white "mountain" coloration on the map. Plains mobs tend not to hang out here. In addition to providing a nice view over the area, such a location remains generally peaceful. The only downside is that this base is not adjacent to water, meaning you would need to separately build a secure port (possibly to export Blackmetal Scrap to a foundry base).