Boric acid 1/4 - 1/2 tsp in 1 cup of Karo syrup. Put out a bunch of little bait stations with this mixture & wait. Bottle caps, strips of wax paper, any small shallow disk, or even coins can work. The biggest secret is not to use too much boric acid. Too much and the worker ants die before feed the babies or queen.

You can also mix the BA with a protein (peanut butter) or some left over grease. This way you can get other ant species that like sweets.

One or the other of those approaches should work. Fire ants will go for the grease and avoid the syrup. Sweet ants do the opposite.

Generally ants are not a big problem in lawns. Cut ants, carpenter ants, and fire ants are a problem to plants and people, but the other ants just go about their business. I found that once I started using organic fertilizer all my insect issues went away.