Patrick of Yoga Garden in Yokohama drew me some of the various yoga poses he recommends for helping people get into full or half lotus posture. It’s right there below this article. After that I put some links to videos of the poses that I found on the Internet. I don’t have any connection with these yoga videos. I just looked for straightforward videos that showed the poses.
These postures have helped yoga people get into the lotus posture for a few thousand years. So maybe you can benefit from them.
Here those some videos I found on the Internets for these poses.