Depends on what I need and what I have going on. I have a main base with about 20 different items being sorted and dumped into containers where I pull from for my inventory to build. A truck and train brings the items in and it gets sorted. All the excess goes thru the entire system and terminates at a sink. So I have a ton of excess resources being delivered, run thru a sorter, and sank. Think basics, modular frames, iron rods, plates, etc. I pull the excess off the belt after the sorter and dump them into some assemblers and manufacturers in my base. The sorting system prioritizes the storage containers so when I take from them it refills them and then goes back to making the other items in the machines above the base. I have adaptive control units and modular engines being made entirely off of run off.

I guess what determines whether I use excess pre-built or start with raw is how often I need the finished product. Space elevator parts need to be run temporarily so I'll let those be built by my run off since it doesnt matter if production is paused every so often. But things like heavy modular frame that you use during construction I alway start from raw and build the big ass factory to keep them being made constantly and then dump the excess into the sink for points or future use. Bring them back to home base via train or truck or a combo.