Workbenches are your friend. Try moving out systematically from your base, digging down just enough to cover up a workbench with wooden floors so things can't immediately get to it. Ensure that the area that shows up with the hammer out is overlapping the radius of the newest workbench, and keep moving outwards. While mobs will wander in from the outside, you put enough ground between the edge and your base that mobs will never bother you except in events.

Build on the border of a black forest to dramatically reduce the danger. Bonus points for having water on a side.
Fulings can be pretty nasty at night, but a border of stake walls will keep most things out.

I just put my crops inside an old Fuling base.. no walls, no anything other than just cultivated land in the middle of it. I never have any issues. I have a portal on a nearby mountain base and just run down there when I need some crops and they are never disturbed.

Never had a problem with a stake wall with a workbench and a portal along the inside walls. Fulings sometimes wander up to the wall when I'm doing something inside, but I just step out and whack 'em. Oh, I keep a chest in there too, to hold the black metal. When I get a full load I run it out to a nearby base I use as a port.

Make a double stone wall + moat in a little field ( like 30mx50m ) , workbench to cover all spawnpoints inside and only mosquitos will bother but not so much
I did like this in my first plains farm

Stakewall + workbenches and camp fires.

workbenches it is, thanks!

When I scouted out a location for a Plains base, I wanted one that was far from any Fuling village, not near any Deathsquito or Lox spawn points and not too far from Black Forest/Swamp biomes.
I settled on this...
https://steamcommunity.com/sharedfiles/filedetails/?id=2426221264
The local Fulings, Lox and Deathsquitos take care of any invasions, so that is never a concern.
The only minor concern is the nightly Fuling patrols, but even they can be ignored because they cannot do any serious damage to my stone walls. Any damage they may do to my fields, fences or mills is easily repaired the following day. So, I ignore the night patrols and go to bed or hop through my portal to get on with stuff in another part of the world.
It may seem an odd thing to say, but I've found this base in the Plains of all places to be the least troublesome of any biome LOL.

I found a little hill on the plains, and then shaved down all the sides until they were sheer. Then I dug a trench around it, even deeper.

I took all the stone from that trench and added a raised lip around the top with the hoe, sort of like a wall.

The entire structure is just the regular ground deformed and reshaped. It's completely impervious to damage. Basically it looks like a little castle from faraway.

I don't even get bothered by deathsquitoes. They seem to bump into the wall.

I am in the process of building a farm on the plains, on the edge next to a swamp. :o)
Its not finished yet but is fairly secure with strong defences (earth wall & moat on 3 sides). I only get intruders during raids (entering from the sea) and the odd deathsquito flying by. Its small but enough to grow barley and flax. I buried wards either side on the coast and that seems to help keep the area quiet and hassle free

https://steamcommunity.com/sharedfiles/filedetails/?id=2786639594