Begin with two open profile sketches.
Solidworks sheet metal lofted bend.
Lofted bends in sheet metal parts use two open profile sketches that are connected by a loft.
To find out more about lofted bends you need to dig a little deeper into help and do a search for bent lofted bends unfortunately at this current time i am only able to find information about formed lofted bends in the solidworks training manual for sheet metal.
The base flange feature is not used with the lofted bend feature.