Clearly, the only way this works is stone walls.
Medieval people did this all the time.
A single person can easily stack bricks, and mortar layer upon layer and start with 3 widths of a modern brick.
Is that enough? Yes stop, if not expand it.
Use field stones, and whatever, to form a castle wall if necessary. These things are like 30 to 50 feet high, and easily 10 foot thick or more.
They were built in medieval times all the time.
Now after you build the initial perimeter, place guards on the top with bow and arrows and other ranged weapons. Beat the animals back till they don't relentlessly attack near the wall.
Then start building a second wall far enough forward to call it progress, but no so far that the previous guards can't defend them from the top of the wall. Expand one or two segments of the wall at a time until you have a usable amount of land.
Clearly, according to the OP, these animals are as plentiful as tribbles (Star Trek) and are going to have to be mass slaughtered for food.
Banks of archers on the wall tops killing them by the hundreds. Then hauling them up, cooking, and eating them.
As soon as you are old enough to hold a bow and arrow, up on the wall shoot at the unending hoards of monsters.
The only way to start a town is hundred of ranged weapon people protecting the wall builders until the walls are big and strong enough to do the defending.
Either that or finding plains that are seasonal, and you can build a wall while the hoards are attacking someone else.
The simple fact, is that almost no animal is battle ready at birth. Needs time to mature, and therefore can't endless attack humanity. Eventually we have to kill enough of them to gain a foothold on the land, or they will kill us all and we won't be alive to need food.
Archers from tree tops to help guard the initial wall builders.
Personally, I would eat well, with 100 arches making a kill every couple minutes 24 hours a day. 30 per hour 100 =3000 24 =72000 and if each one only has 2 pounds of usable meat thats 144,000lbs of meat per day.
To heck with farming!!!!
update:
Additionally your going to need a pit, wide enough so no creature can jump it, and deep enough so the creatures are at least permanently trapped. Even better if they die from impact with the bottom.
This is necessary to prevent being swarmed, and provides an additional layer of passive defense.