Elevated One Leg Pike Stretch
This is my favourite hamstring stretch for beginners, as it is easy to learn and properly isolate the hamstring, easy to measure progress, and has a good active mobility counterpart, the one leg pike lift-off.
To perform, place your leg on an elevated surface with your leg straight. The surface should not be so high that you can’t stand up straight. If you have to lean back in order to keep your leg locked out on the surface, the surface is too high for your current mobility.
Once you are in position standing up straight, at an appropriate height this should already be a moderate stretch. From here, lean forward to intensify the stretch.
This set-up can also be used to perform a regression of a front split by increasing the distance between the front heel and back foot. This will load the front leg in a similar way to the front split, adding in an isometric strengthening component as well as the stretch. It will also be a much more intense stretch, so be careful, and also give your self something to hold on to if you need support when getting out of the stretch.