I've made a base at a Sentinel pillar on a planet that spawns tons of curious deposits. It's called HTK_Nanite Farm.

Arrive, shut down the sentinels, and go looking for curiuos deposits. You can rack up around 200,000 runaway mould in about ten minutes, 9999 will refine into 1999 nanites in twenty minutes.

I've marked 5 locations with save beacons, all <1000u from the base. You can see 4 of them in the pictures.

The curious deposits respawn after about five minutes so by the time you've found three, you can go back to the first and just repeat.

The base has thirteen refiners, so you should be able to refine 25,987 nanites every twenty minutes. The refiners are in the round rooms around the landing pad, but you need to use the teleporters in the teleporter room to get to them, or unlock them from the command room overlooking the landing pad (with the flag on it, above the airlock). To get to the teleporters, go through the airlock using the switches, and it's behind the reception.

If you feel like exploring, harvest atlantideum whilst the sentinels are shut down. Refine 1/3 of your atlantideum into pugneum, and you'll get equal amounts of atlantideum and pugneum, refine them together to make runaway mould. 9999 atlantideum will net you another 4000 nanites.

There's also a traveler's grave right next to the furthest away curious deposit, behind a floating island. There's also a depot over the valley which you can see from the lounge.

If not, feel free to relax in the base whilst you refine. It's fully equipped with a kitchen, bedroom, storage container [0], trade terminal, and roamer station, with nice views from the bedroom, lounge, and dining area.