I added slabs to the voxel engine the other day and this video is showcasing that. There is still some things to be done with them but they look pretty good here.
Also, Alpha 1.0 of the engine is finally out and amiable on GitHub!
https://github.com/Divine-Star-Software/DivineVoxelEngine
source
Are you aiming to make this engine one akin to how minecraft works, but more advanced?