Garbage disposal flange is leaking
The flange coming out of the disposer secures the pipe that attaches to the drain. There is supposed to be a rubber washer behind the flange that when the flange bolts are tightened seals the pipe connection from leaks.
disassemble once more and verify there is a washer behind the flange. If not get one and skip the putty.
If the leak is from the sink basket where the disposer attaches at the sink bottom it may be due to:
-not enough fresh putty. The putty should be rolled to a 3/8-1/2 inch diameter and overlapped where 2 pieces are used. More is better in this case.
-press the basket into place before tightening the screws underneath. You should see putty being forced from under the baskets flange in a continuous ring.
-the sink edge for the basket is bent or damaged. check for burrs or lippage with you finger.
-the basket screws aren't tight enough.