The Nordic Curl is a key component of hamstring injury prevention programmes in elite sports but is still a relatively underutilised outside of that environment. The key component of the exercise is the lengthening, eccentric (negative) phase. This is where all the benefits of the exercise can be found, and they can have a profound influence on improving your hamstring mobility without the need for traditional static stretching.
Zip up your abdominals
Actively engage your glutes to help control your back
Control through longer ranges
Targeted muscles trained
Biceps Femoris short head
Key movements trained
If you are struggling to lean forwards using the whole body and are hitching at the hip that may be movement issue or indicate that this exercise is bit too advanced. Perhaps build in to this pattern using a regression like the Nordic Hold.
If when attempting this exercise you feel it more in your lower back, think about your form and whether you are arching (extending) your back as you move through range, this can often be because your back extensors are attempting to take more load and you may have to active tuck your pelvis under (posteriorly rotate your pelvis) to help reduce the work of the back itself and put more into the hamstrings.
The real gold of this exercise are in the longer ranges, so slowing down the outer range (as your chest is closer to the floor) is where you'll get the most of the benefits associated with the exercise.