Two kinds of build guide. Both are step by step, both work for 1 or more builders, and both give every builder their own plot.
Everybody follows the same instructions and builds the same unit in their own plot. Line the plots up and the units join into something none of you could have built alone — a viaduct, a street, an avenue of ideas.
The same step format, for builds that have to actually work: doors, farms, sorters, lamp screens. Extra layer views for the wiring underneath, and a test you run at the end of every build.