use a massive height advantage

you can be drastically lower than everything, just make sure to dig out a cliff and be on the coast.

and then put workstations everywhere, get stonecutting going (you'll have plenty of stone from digging rock)

Create a "panic" portal. Put one down in your base label "panic", then keep the items to make another one anywhere. If you feel yourself getting overwhelmed you can always just go through the portal and then the worst thing that could happen is that the other portal gets destroyed.