So with the original entrance, the trapped insects could easily walk out again, with this design, I added a lip, to prevent them from escaping.
It is quite effective, in the photo you can see the trap after only three days, with the original entrances there were only like 5 to ten flies trapped, after two weeks.
I've printed this in PETG with supports on, in order to support the overhanging locking mechanism. Make sure to completely remove the supports, to get a good fit.
The author marked this model as their own original creation.