Air Carrier First Officer reported not being properly configured for approach to LAX under 1;000 ft.

Narrative

This report is in regards to a Too Low Flaps Warning on final approach into LAX. LAX was shooting ILS approaches to [Runway] 25L; though we had visual contact with the runway at least 3 miles out. The approach to landing phase is always a high workload time at LAX. As we were configuring for the approach there were calls to spot traffic landing on [Runway] 24R; landing clearance from Tower; and focus on the proceeding landing traffic to confirm it was cleared of the runway. Though definitely a high workload phase; these are all normal distractions. The Captain was Flying Pilot; and configured the aircraft on profile till we reached flaps 25. At this point we waited for the aircraft to slow to the flaps 25 speed. Flaps 30 was not called for; and we continued our descent on the approach. We were both focusing on the runway and the proceeding aircraft; and forgot to configure flaps 30 for landing. At approximately 400 ft. we received the Too Low Flaps Warning. The aircraft was on speed; glide path; and in VMC conditions. The decision was made to extend the flaps to 30 degrees; and the landing was made normally. After arriving at the gate; we debriefed the situation; and both agreed that we should have done a missed approach; as is SOP for a configuration warning at that phase of flight.Contributing factors to this event were normal distractions in a high workload part of flight. A mind set of getting the plane on the ground when you see the runway right in front of you; and you are on profile with path and speed. Lastly for myself; complacency. I land visually; daily in LAX. As the Monitoring Pilot; I should have been more focused; and caught the we were not at our designated landing flap setting. In the future I'll be more vigilant; and call for a go around if I find myself not configured for the approach correctly under 1;000 ft.