In the past a made a minecraft style spaceship building game - infact I am still busy with it. I had the same problem you had and the way I got around it was using a “Aim Block”. This is how it works:
Create a duplicate of the object you are placing
Instantiate the object and let it follow around your mouse cursor.
Slightly decrease the collider size.
If it is not collidign with something then allow the real block to be placed at the same location