I have my first kitchen with an upper corner cabinet with a 45 degree face. I plan to use the 20" diameter lazy susan from Rev-a-Shelf in this cabinet and want to make sure I size it correctly. When sizing the opening of these cabinets, should I just make the box opening something like 20-1/2" wide, keeping the side walls the same depth as the adjacent upper cabinets - 12"? Is there an argument for making the opening wider or narrower than the 20"? I'm thinking that extra volume inside that box might be bad since there's more space for things to fall off the susan and get lost in there. If I made the opening narrower than the overall width of the susan I suppose I'd have to install the susan before assembling the box, but then it may be impossible to remove it should it fail someday.
From contributor A:
Since you say this is your first diagonal wall cabinet, you may or may not realize how sizing the opening works. If you have a wall cabinet that is say 24" in width by 12" in depth your opening is going to be somewhere around 17". The only way to change the opening size is to change either the width, or the depth, or both. If you already understood that, then I might have misunderstood the question. Either way I strongly recommend drawing out your cabinet footprint full scale to see how it will turn out.
As for the lazy susan, I have never used one in a top cabinet. I believe they are the same as the base units though. They are installed after the cabinet is built, and assembled in the cabinet, which means your opening does not need to be 20" to install.