Creating an RTStruct file with contour data

I know that it is possible to use SlicerRT to import a Dicom RT file with contour data (There are tutorials out there which I just worked through). I currently have stack of CT images, with contour data in an SR file. If I would like to load this into Slicer, do I need to translate the SR file into an RTStruct, and then load from there? And if so, what fields need to be present? (I’ve tried creating a minimal RT file with just the header data and the contours, but Slicer won’t accept it)

Operating system:Windows 10
Slicer version:4.10.2
Expected behavior:
Actual behavior: