I love California Poppies. I tried to grow some right after we moved in an a bit of hill, used seed, but I think they did not like our clay.

As you said, I would wait until they set seed and then spread it where you want it, Good luck.

Very pretty,hard to think of them as a weed.

I miss them so! so good to see them again. Enjoy them enough for me. Gorgeous.

It's one of those spring things. Ya gotta know what they look like and then dig deep. Move as much as you can, including whatever root structure there is. Have the new spot the same size and depth as the dug out stuff. Move the old to the new and the new to the old. Water the first coupla weeks. You should get about 35% success.

I have volunteer CA poppies all over the place, even in my garden boxes, They are so pretty that I let them stay until they start to seed, then I'll pull them, but they come back the next year.

Lilo, I think you have right idea in how to grow some poppies to another place, BTW, I don't do any kind of preparation to the soil where the volunteers appear.
As an aside, in the 40 years we been in this house, I've found them in everywhere, except the lawn.