I use the poor mans’ GHR: Get a lat pulldown machine, face away from it, & slip your feet under the thigh pads… (hard to explain but hang in there)When you are in position the backs of your calves should be UNDER the thigh pads and you should be either kneeling facing AWAY from the lat machine on the padded cushion w/your knees or assuming a pushup position from that stance.
From there SLOWLY lower yourself down while “gripping” the thigh pad with your calves or ankles. Then, explode up with good form using your hammies to lift you with your back in its normal curve. It sub par to a true GHR but they work for me Most gyms & personal trainers have NO CLUE as to what a GHR even is lol & no gym nearby to me has one either
The other option is to have someone hold your ankles while you perform the movement & you do them off the end of a raised platform/bench if you wish to add weight.
There are also a hell of a lot of supplemental exercises from contributors on this site dedicated to building up hamstrings (e.g., Thibodeau, Waterbury, etc.)
Hope that helps. Try Youtubing GLUTE HAM RAISE for more ideas.
(After hitting submit I see Joe Joseph already submitted the same type of answer Oh well)