Roll out on a Final at say 1 nm and 500 ft, select the attitude /power combination that you require for the approach.
Note where the landing point is in the windscreen - by maintaing this in the same position you musy fly a straight line towards it.
If everything else remains constant, the IAS will also remain constant however, in practice it will vary due to changing Met; maintain IAS with throttle.
The net result is a smoother, easier to fly approach with a linear descent path.