In Easy Seated Forward Bend (or cross-legged forward bend) you sit with your legs crossed and tilt your pelvis forwards so that you ribcage moves towards the floor.
If you want to work at stretching your hamstrings (which generally involves tilting your pelvis forwards relative to your thigh bones) you can use this posture to practice tilting your pelvis forwards
However, prior to bending forwards, you may find it helpful to first practice tilting your pelvis forwards and backwards while sitting upright.
To feel your pelvis first practice rocking it forwards and backwards while keeping your ribcage upright. As you rock your pelvis forwards allow your spine to bend backwards. As you rock your pelvis backwards, allow your spine to bend forwards.
In both cases, feel the movements of your sitting bones, pubic bone and even your hip crests. Then try to feel the entire mass of your pelvis as it rolls forwards and backwards.
Once you've got the hang of feelng your pelvis, then roll it forwards and allow your ribcage and arms to move forwards.
Try and keep your spine reasonably straight while doing easy seated forward bend. To give yourself room to sink down reach your head, arms and ribcage forwards, away from your pelvis.
Once you've lengthened your bodythen you can allow your ribcage and head to sink down whilst allowing your spine to bend forwards at the same time.
You can work towards feeling your body reach forward one element at a time in time with your breath.
Note, if you have difficulty tilting your pelvis forwards in easy seated forward bend you might find it helpful to sit on some books or a block.
You could also focus on reaching your ribs and head away from your pelvis. That may mean that you end up reaching upwards more than you reach forwards! If that is the case, then practice sitting upright as tall as possible. From here then work at increasing your ability to tilt your pelvis forwards. And then relax.