Factorio

Add more roboports where you want them to be.

If I wanted a solely bot-baaed network, I would seperate ores into their own network like slazer suggested, but also make a solid line of roboports within the network. The robots flying to distant roboports tells me theres not enough roboports, so add more until they stop doing that.

And also, I agree with direct insertion to furnace being the way to go. I'd also make gears and steel at the ore patch, too, because both of those take multiple iron plates. Getting 1000 gears into your main base, at the max cargo size of 4, takes 250 bots carrying gears but 500 of plates, and 1000 steel is 250 bots of steel but 1250 bots of plates to then smelt.

If I was building a botmall, I'd also try to put them wherever the most expensive component was. Even if they're not directly connected to production, if I can minimize the trip it'll be way more efficient.