Find a nice flatish spot in the meadows with a small hill top. Pick down as far as you can in the center of the hill. Flatten out the rest of the hill and then raise the surrounding area to the flattened level and expand that out until the edge is 8 meters above the surrounding area (max height). Place a horizontal core wood pole (4 meter) for a tightrope bridge and walk across it. Put 2 gates where the corewood pole ends (one on either side) and then raise an 8 meter earthen berm all the way around your base leaving that 4 meter gap between the berm and the "base" of your base.

This will give you an indestructible earthen wall around a 4 meter wide (and potentially 8 meter deep) dry moat with the "base" of your base 8 meters high on the other side of the moat. (You can take the gates out after that). Mobs can't tightrope the corewood pole but might fall into the moat at the gate but they won't be able to climb back out and you can just plink them with your bow.

If you need to get a cart across you can build a 2 wooden floor tile wide bridge on top of the corewood beam and then dismantle the floor boards once the cart is across. You can put a wooden stake wall or a stone wall all the way around the "base" of your base to stop thrown rocks and you can put your live stock under a roof to make sure that they are safe from areal attacks until you can deal with the flying critters.

https://steamcommunity.com/sharedfiles/filedetails/?id=2845923276
https://steamcommunity.com/sharedfiles/filedetails/?id=2853688768

You can also go the other way and start in a shallow hollow and pick down 8 meters and flatten all the way out. Go out 2 tiles and pick down for a 4 tile wide moat. Then the inside wall is the earthen berm.