Earthen wall + stone platforms extending outwards is what I use.

First works fine for my meadows farm by the forsaken altars and also worked for my plains farm though if I got seeker raid at that location I'd have to run out and distract them since it was made before killing Yagluth.

Final base is the combination of earthen wall and the stone platform wall on top of that with the only way to get in is via jumping from a stone stair that I made. 1 seeker got in because I was looking at it from above on my wall so if you ignore them then I think they won't be a problem and just hang outside until the event is over.