Lower back pain lifting program

Maintain neutral spine, push bum back to lengthen hamstrings then facilitate the stand motion with focus on hamstrings and glutes.

Use box or bench to set height if needed (may need to chock this up as you're tall). If back is straining try leaning trunk forward more during the movement - this will increase the amount of work at the hips and decrease the demand on the lower back.

Bent knees, bum up to form an "L" shape, maintain knees inline with body. You can do this with your legs straight out instead, this will reduce work demand of the quads and glutes - knees bent = more work.
Palms down will be more upper back focused, palms up will increase work at the biceps.

Try to keep gap between bench and lower back as small as possible (does not need to be closed completely). Arms as straight as possible.

Try variations of this, these include:
Pulling from the hips - more hamstring and glute focused, there should be little to no movement in the back here other than that it is following from the pull at the hips
Extending using back -
This is where you'll extend fully using your back - this variation can feel a bit uncomfortable, especially because you have lower back pain.
I recommend trying both and finding which works for you - or a combination pulling from the hips, extend the back slightly at the very top of the movement to incorporate work at the lower back.
You can also use a dowel or broomstick on your shoulders to add rotation at the top of the movement.