If you're already making your own laundry soap, or using borax for another reason, then you already have the poison you need to make your own ant poison. The only other ingredient you need is honey. This recipe of course only works on sweet ants.
Find a milk cap, jar lid or other throw away lid to mix the poison. I used the top of a frozen juice container. You want something the ants can crawl in and out of to take the poison back to the nest. Sprinkle a little bit of borax into the lid. I used maybe 1/8 tsp. Then pour a little honey, about 1/2 tsp. It doesn't have to be accurate. You want enough poison to kill the ants and enough honey so they take the poison. Adjust as needed.
I placed my lid in the bathroom where I discovered the ants coming through the crack on the floor where the shower was installed. Before I put the poison down I had a few ants wandering the house. Within an hour of placing the poison word got out to the ant nest "food" was nearby and it seemed the whole nest came to eat.
Less than 24 hours later I found two ants left. This stuff works!
Please use caution as you would any store bought poison. The borax is still toxic to pets and children when ingested. Thankfully my two cats didn't find interest in all the ant sized commotion.