The base flange feature is not used with the lofted bend feature.
Solidworks sheet metal lofted bends.
Under manufacturing method select bent.
Look at part tree.
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.
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.
Click lofted bend sheet metal toolbar or insert sheet metal lofted bends.
Your simple sheetmetal bend is ready.