I am trying to create a box via sheet metal. Hands free so that all I need is length, depth, height. I have the base flange but I am having trouble creating the edge flange.

The sample code precondition is that an edge is selected what the point?... If I wanted to that I could create it manually. I can get the edge and then I need to input a dimension into the flange length to get it to create? Any help?