I haven't had sciatica pain, but I have had occasional lower back pain from lifting things wrong.

I found this video a while ago, and can now routinely touch my toes for the first time ever, and I can just about pike
https://www.youtube.com/watch?v=HhEqFa9lT80

Around the same time I started doing dumbbell dead-lifts to strengthen my hamstrings, and it's made a significant improvement too.
https://www.youtube.com/watch?v=Ipi8_vz8_z0

Since adding these (and other general stretching and core strength workouts), I haven't had any back pain.