Another option is to specify a user-defined position for the haunch. Just press the ESC-key after the command has been selected. The program prompts you now for the intersecting point of the base boundary line with the upper flange that you have to select by clicking it (consider using the virtual intersecting point without Z). Finally, click the approximate direction of the haunch.

The haunch is now created at the specified position and you can dynamically adjust any of the settings in the dialog. Any shape adjustments have to be carried out manually, of course.