This is what it looked like before the felt was added. You can see the felt of the existing roof complete with moss (later removed)
Here is the felt being laid...
Once the boarding was robust enough, the felting was fairly easy. This is started from the bottom of the roof so that the next layer overlap joint was over the top to allow water to run off, not under a layer
The same layer from the other angle, showing it continuing up over the old roof in one piece.