On go the rafters.

The rafters were made from more of the 3x2 timber. The angle from front to back was very shallow so no bird mouth joints were required.
The lengths were measured and cut then screwed down to the upper ring beam using 4in screws. We set the gaps at 24in intervals so that it would be just right for the 8x4 OSB sheets to drop onto. Accuracy is important otherwise error would become compounded and the sheets require adjustment.
The rafters were attached narrow side down maximizing the strength of the wood.