Mix 1 cup of molasses, 2 packets of dry yeast, and 1/2 cup of sugar together and layer onto cardboard and place in area with ants. The yeast will kill the ants, but is safe for everyone else in the home including pets and children.
There is not really a need to go to the trouble. There are many highly effective (although kind of expensive) fire ant baits readily available. The poison in them is completely organic (boric acid)...