I’d like to get into the habit of doing daily yoga to help my back because I had struggled from sciatica. What are the best stretches to do for this and to tone my core and strengthen it?

There are a lot of options to choose from go to youtube I personally follow Sarahbeth yoga she has few sets for back issue and sciatica.

Gentle stretches like the knee-to-chest stretch, pelvic tilt, and pigeon pose can help relieve sciatica pain by reducing tension on the sciatic nerve. Focus on slow, controlled movements and avoid overexertion. Harvard Heath site has great pics and details: https://www.health.harvard.edu/pain/sciatica-gentle-stretches-to-help-relieve-pain-and-improve-mobility

I found nerve gliding exercises to be very useful for my sciatica. Also they tend to be easy to do so a good way to kickstart on the streching part, often with only a couple of minutes. From there I would suggest to expand into stretch/yoga exercises that you like. I had trouble getting motivated to stretch in the morning until I ditch the routines I found and I did only the exercises I liked… It felt so much better that now I’m expanding my routine and building the habit of stretching when waking up… The day just feels better that way!