The base flange feature is not used with the lofted bend feature.
Solidworks sheet metal lofted bends.
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 bent manufacturing method creates real physical bends rather than formed geometry and approximated bend lines in a flat pattern.
Your simple sheetmetal bend is ready.
Lofted bends in sheet metal parts use two open profile sketches that are connected by a loft.
Begin with two open profile sketches.
Set bend radius to 0 03in and k factor 0 5 and ok.
To view this part in flatten form click sheetmetal flatten.
Under manufacturing method select bent.