Thanks for all the replies but there is still no real "solution" to my problem.
The way it's described in the youtube video from FireSpark81
called "The Ultimate Guide To Chickens In Valheim Mistlands Update"
is simply not working for me in any way. The only way they lay eggs at all now is to have a large enclosure with only some chickens. and then they also only lay 2-3 eggs at a time
(enclosure ~ 12x12 with 10 chicken)
I recommend everyone answering in this Threead to watch his youtube video so you guys understand what the problem is.