I've tried to find an official U of M document on oriental poppy propagation but am failing. I can tell you what I've done for poppies in my garden though. I don't think what I had was oriental poppies but from what I can see it's all the same, though oriental ones might be a little fussier.
I have had "great luck" not harvesting seeds and letting them self sow wherever they fall. My entire vegetable garden ended up in poppies one year because of wind. It was gorgeous, but probably not what you're looking for.
There are like a zillion poppy seeds in each of the seed heads--what I've done is just sprinkle the seeds in the area I want them to come back up, mix them just barely into the top of the soil and then wait for them to sprout. Eventually, I thin the patch down to a manageable number, getting rid of the weak looking ones and ones that are growing outside the acceptable area.
I believe poppies need the cold season to "cure" properly so they grow, I can't find the term for that. You can either plant in the fall and they'll cure in the ground OR you could store your seeds in a cold place (I kept mine in my charcoal grill one winter, figuring critters wouldn't get in it.) and plant them in the spring. Either should work--maybe do a little experiment to see which works better for you.
The other thing I read that I didn't know and is possibly helpful is that they're going to do better in sunnier spaces. I knew they are sun plants but hadn't thought about it consciously before so it seemed worth mentioning.
Let me know if you have other questions and I can do some additional digging.