Hi John, I’m the person who designed that clamp – well, I mashed together two parts other people had designed. It’s been a while since I did mine, but looking at it, I know I must have used support to print it, and probably spent some time digging/cutting out the support. If you have options for support in your slicer, you should try playing with the support settings to try and get the minimum amount of support possible, so it’ll be easier to remove.
Sorry I don’t have more details. Like I said, I did mine quite a while ago. It does work well when finished though – it’s what I use on my setup.