When would the large work force of farmers be available to work on government projects like building palaces and tombs?

The large workforce of farmers would typically be available to work on government projects during the off-season, when agricultural activities are minimal, such as after the harvest. This period varies depending on the region and climate but generally falls in late autumn or winter. Additionally, farmers might also participate in such projects during times of economic need or if incentivized by the government through payment or food provisions.