Hip Thrust Technique

I want to like this movement and include it in my program since I tweaked my low back the other day doing RDLs, with hip thrust and 45 degree back extensions being my hip extension movements in addition to seated leg curls. The problem is the movement feels very unstable even with only 55lbs on the bar. In the past when I tried doing them I slipped and kind of slammed my low back into the floor, with people rushing up to me to see if I was alright. After trying again to do them today I just settled with barbell glute bridges on the floor. Is this maybe a bench height thing, or should i raise the bar on some plates to limit the ROM? I think the ROM with my frame makes the movement feel unstable. I tried to really dig my shoulder blades into the bench but it still feels awkward and like I could slip again. It’s light weight, so I’m not sure if it’s a loading issue.

Hard to say without seeing exactly what happened, but there’s always going to be a bit of “instability” with a new movement until it becomes more practiced.