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Civil engineering types ran some of the larger scale solar projects for a major contractor as delivery/construction/execution managers along the Murray river a few years ago.

Site prep, Clearing, Grubbing, site excavation, trenching, pile driving were big ticket items, mechanical assembly of the trackers, mounting of the panels, landing of very heavy inverters & transformers & their pads, staging co-ordination of hundreds of thousands of solar panels & containers, even the HV cable runs are heavy machinery dependent.
There is a fair amount of labour required for the tracking assembly & mounting panels on the trackers.

The electrical installation component happens more towards the end - much like a house fit off - laying cables in trenches, connecting panels, fitting off Cables from combiner boxes to inverters, string cables etc.
As with the above, the major labour component is related to plug & play connection & cable tying/conduit installation related to the PV panel strings.

Then commissioning - but not a big labour component & not a long time to do this.

Solar PV farm design is a well trodden path & supply chains mature.