Get a medium to large metal coffee can, or any old metal can I guess. Make sure it's cleaned out and dry to start with, and is not rusty.

Then get some spray cooking oil and a few scraps of bread. Spray the inside of the can with cooking oil, then drop some bread scraps in there.

Now you have a roach trap, set it near where the roaches are generally at their worst, and they'll crawl out of the walls and into the can to get their munch on, but won't be able to crawl back out.

Check it every couple or few days or so, eventually the roaches will start piling up and most of them that have been in there for a bit will end up dying because they're covered in the cooking oil and apparently can't absorb oxygen.

Take the trap as necessary and either dump it in the toilet and flush them away, or if you have access to a bonfire burn pile, bag the little demons up and burn them. Then clean the can out and reset the trap as necessary.

Even with the worst infestations I've ever seen, this tends to eliminate over 99% of them within about two weeks, if not less.

A few thoughts about the different approaches between my trap vs poison...

If you poison them, then they just go back into your walls and die, further stinking the place up, is more dangerous to people and pets, and honestly isn't even nearly as effective as people would hope.

But roaches are simple and stupid. They're really easy to trap, and why the hell would I want them going back into the walls in the first place? Especially when I can just flush them instead?