Over the years, SOLIDWORKS has really improved the ability to create complex sheet metal parts. With this ability in the past, you would be somewhat limited with the flat pattern that was produced. It may give you a flat pattern that is in an orientation that you may not have chosen. (see below)
You will notice in the second screenshot that the flat pattern fixed face is the angled face. This puts the flat pattern on a weird angle as shown in the third screenshot.
In SOLIDWORKS 2015 you now have the option to change the fixed face and how the part is flattened. First, flatten the part. While part is in the flattened state, right click on the flat pattern1 feature and edit feature.
This will take you to the properties dialog box that will allow you to select a new fixed face that will change the way the part is flattened.
Now the flat pattern will flatten from the new face.
This option helps you create complex parts and lets you determine how the parts are flattened.
Field Technical Services Manager