I am trying to create two different framed angled wardrobe. The smaller one is a fully slope so i used modify -> Single Slope Top to angle the cabinet. I am then able to create a 100mm frame all the way around the Wardrobe to be used as fillers so they can be used for scribing on site. 

The Second Wardrobe is wider and required a flat top of 1000mm and then a 35 degree slope. In this case I am unable to create an upper strip external zone and unable to allow for this is on the cabinet. 

Please can you advise either what I am doing wrong or if there is an alternate method for this.

Thanks Dan,