The way I taught Keeda how to go down was by sitting on the floor with my feet on the floor in front of me and legs bent at the knees so that she could just get under them. I got a treat and lured her under my legs with it. She'd have to crouch down into a crawling position to crawl through my legs. When she was under, I'd gently push my legs down so that she had to stay under them in a laying position, gave her the treat, and praised. It only took her a little while to "get it"