Is there a way to create non-procedural blocky terrain?

So I'm relatively new to Unity and C# and I'm working on a game with a sort of Cube World-esque aesthetic with the blocky voxel terrain, but I don't want it to be procedural. I'm not going for an infinite map. I found one tool on the asset store that would ordinarily be what I'm looking for, but I'd honestly like to avoid spending money on the asset store if there's a better way to just do it by myself. To my knowledge, it doesn't seem like Unity terrain seems to support sharp 90 degree angles like would be needed for the look I'm going for, even if I converted the mesh I'm using into terrain, so for now I'm stuck with just using an fbx file I exported from Blender. Is there any way to achieve this sort of look with standard Unity terrain to allow for easier editing and detail painting?

I've attached a picture of the kind of look I'm aiming for just as a reference

8735103--1182528--Island.jpg

An idea or shot in the dark... Check out this free asset: https://assetstore.unity.com/packages/tools/terrain/terrain-creator-low-poly-146834. Looks kinda close, but its free and you might be able to adjust its settings to get the look you want...