hit.transform.position + hit.normal; makes objects float

I'm not 100% certain but usually normals are unit vectors (length 1) so with this code you're placing the object 1 world unit in front of the collision spot.

@NoseKills I see. Do you know how I could make a workaround for this? I am clueless.

Just remove the + hit.normal position, and if your cube has a scale of 0.1 and originally had a height of 1 unit, then instead of that code, just use:

 Vector3 newPos = hit.transform.position;
 newPos.y += 0.05f;
 addCube.transform.position = newPos;

@Evil Tak But what if I want the object to be on all sides?

How can Object A be on all sides of Object B?