Hi all,
I am pretty sure i first wasn’t able to do this but in the 180 build it is now possilbe to build wall mounted stuff onto slab buildings.
I tried this before in earlier builds but wan’t able to do that on that time. I am not sure how long this is possible but would like to thank radiant entertainment for doing this 
Now i can finally make custom buildings from slabs and even put wall accessories on them!
So Thank you <3