Storm Circuit makes a lot of large PCB from 2 layer to 12 layers.Usually ,PCB dimension is about 100*200mm, or more .the length is over 400mm,we can call it big, large means length over 600mm.
The longest board we made is 1200mm board ,it is LED projection ,T5 tube.
12 layer PCB,we made was 564*502mm, 8 layer we made was 1072*488mm, this is very difficult to do as most of the equipments can not stackup so big board.
Examples of what we did for large PCBs
Mullilayer standard stack upstackup.pdf
PCB Fab check list
Flex PCB material
High frequency material
Heavy copper PCB
20 layer PCB
10 layer PCB
Quick Turn boards