I used to find with students having your problem that two things would help them in addition to what has been stated in previous replies.
1/ A thorough re briefing or a session or both on stalling. Pointing out attitudes for a gentle stall but mostly the feel of the controls and their effect on the aircraft as the speed decreases.
2/ Then I would demonstrate on the approach that the flare does not have to happen in one go. If the approach is done at the correct airspeed then you have plenty to spare as you approach the ground. So at about 10 to 15 feet above the ground I would apply a little back pressure ( reminding them that the elevator is sensitive at that speed ). That would slow the aircraft a little but more importantly it would slow down the rate of descent. So now the ground rush is much less severe. Then you can flare at the correct height and again remembering to be gentle at first but as the airspeed decreases to the stall you need to be more positive with the controls.If done right the stall warner will sound and the main wheels will touch. Do not release the (by now) full back pressure or the nose will bang onto the ground.
It seemed to work for me and all my students landed that way and some even progressed onto tail draggers with little effort.